From 21a4c70bb7886cb0f3565157880fcfbf35473757 Mon Sep 17 00:00:00 2001
From: albert <92109627+Albkat@users.noreply.github.com>
Date: Tue, 5 Dec 2023 19:02:16 +0100
Subject: [PATCH] format geometry_optimization

Signed-off-by: albert <92109627+Albkat@users.noreply.github.com>
---
 optts.f90                 | 126 +++++++++++++
 src/axis_trafo.f90        | 198 ++++++++++++---------
 src/geoopt_driver.f90     |  99 +++++++----
 src/main/property.F90     |   2 +-
 src/model_hessian.f90     |  27 +--
 src/optimizer.f90         | 363 +++++++++++++++++++++++++-------------
 src/setparam.f90          |  11 +-
 src/splitparam.f90        |   4 +-
 src/type/anc.f90          |   6 +-
 src/type/setvar.f90       |  46 +++--
 test/unit/test_thermo.f90 |   4 +-
 11 files changed, 596 insertions(+), 290 deletions(-)
 create mode 100644 optts.f90

diff --git a/optts.f90 b/optts.f90
new file mode 100644
index 000000000..a5cb69207
--- /dev/null
+++ b/optts.f90
@@ -0,0 +1,126 @@
+subroutine optts(n,at,xyz,q,qsh,nshell,z,cn,nel,nopen,nbf,nao,P,wb, &
+   & kspd,gscal,kcn,xbrad,xbdamp,alphaj,d3a1,d3a2,d3s8, &
+   & d3atm,egap,et,maxiter,epot,grd)
+   
+   use iso_fortran_env, only : wp => real64 
+   use setcommon
+   use splitcommon
+   use atmass
+   implicit none
+
+   integer :: n,at(n),nel,nopen,nbf,nao,icall,nshell,maxiter
+   real(wp) :: xyz(3,n),epot,wb(n,n),q(n),z(n),kspd(6),et,egap
+   real(wp) :: cn(n),grd(3,n),qsh(nshell),P(nao,nao)
+   real(wp) :: gscal,kcn(4),xbrad,xbdamp,alphaj,d3a1,d3a2,d3s8,d3atm 
+
+   real(wp),allocatable:: coord(:,:), freq(:), u(:,:), uu(:,:)
+   real(wp),allocatable:: xyza (:,:,:), rmass(:), e(:), e2(:), geo(:,:)
+   real(wp),allocatable:: coord0(:,:), displ(:), xyzmin(:,:), bmat(:,:)
+   real(wp),allocatable:: x(:),b(:),c(:),d(:),xx(:),yy(:),yy1(:),yy2(:)
+
+   real(wp) :: norm,thr
+   integer :: i,j,k,m,n3,ii,ia,ic,isave,nprj,mode,maxoptiter
+   character(len=2)  :: asym        
+   character(len=30) :: fname
+   logical :: ex,fail
+
+   thr=-10.0_wp     ! modes below this value are projected out !
+   mode=tsroot+6
+   fname='xtb_normalmodes'
+   
+   write(*,*)
+   write(*,'(7x,''======================================='')')
+   write(*,'(7x,''|       T S   O P T I M I Z E R       |'')')
+   write(*,'(7x,''======================================='')')
+   write(*,*)
+
+      
+   write(*,*) 'normal mode file    : ',trim(fname)
+   write(*,*) 'root for TS         : ',mode    
+
+   ! error section
+   inquire(file=fname,exist=ex)
+   if (.not.ex) then 
+      write(*,*) 'run -hess first!'
+      return
+   endif
+   
+   !> DoF
+   n3=3*n
+   allocate(freq(n3),u(n3,n3),rmass(n3))
+
+   ! read normal modes !            
+   ! normal case !
+   open(newunit=112,file=fname,form='unformatted')
+   read (112)k 
+   if(k.ne.n3) stop 'severe read error on modes'
+   read (112)freq
+   read (112)rmass
+   read (112)u   
+   close(112)
+   
+   ! remove masses from normal modes and re-normalize !
+   nprj=0   
+   do m=7,n3
+      norm=0
+
+      ! loop through the atoms
+      do ia=1,n 
+         ! loop through compnents
+         do ic=1,3
+            
+
+            ii = (ia-1)*3+ic
+            u(ii,m)=u(ii,m)*sqrt(ams(at(ia))) ! remove atomic masses 
+            norm=norm+u(ii,m)**2 ! renormalize
+         
+         enddo
+      enddo
+      
+      u(1:n3,m)=u(1:n3,m)/(sqrt(norm)+1.d-12)
+      if(freq(m).lt.thr) nprj=nprj+1
+   enddo
+
+   allocate(uu(n3,nprj))           
+   k=0
+   do i=7,n3   
+      if(freq(i).lt.thr) then       
+            k=k+1
+            uu(1:n3,k)=u(1:n3,i)
+         endif
+      enddo
+
+      maxoptiter=25           
+      isave=micro_opt
+      micro_opt=1000 ! no coordinate update in ancopt
+
+      write(*,'(''frequency /cm-1      :'',F12.2)')freq(mode)
+      write(*,'(''maxiter (opt)        :'',i5   )')maxoptiter  
+      write(*,'(''optlevel             :'',i5   )')optlev
+      write(*,'(''# of projected modes :'',i5   )')nprj       
+
+      open(unit=112,file='.xtbtmpmode',form='unformatted')
+      write(112) nprj
+      write(112) uu
+      close(112)
+
+      tsopt=.false.
+      call ancopt(n,at,xyz,q,qsh,nshell,z,cn,nel,nopen,nbf,nao,
+     .        P,wb,kspd,gscal,kcn,xbrad,xbdamp,alphaj,d3a1,d3a2,d3s8,
+     .        d3atm,egap,et,maxiter,maxoptiter,epot,grd,optlev,
+     .        .true.,fail)
+
+      call system('rm .xtbtmpmode 2>/dev/null') ! normal operation
+      micro_opt =isave   ! back to default
+      tsopt=.true. 
+
+   !     call system('mv hessian hessian.xtbtmp 2>/dev/null') ! don't use hessian in ancopt
+
+      call ancopt(n,at,xyz,q,qsh,nshell,z,cn,nel,nopen,nbf,nao,
+     .        P,wb,kspd,gscal,kcn,xbrad,xbdamp,alphaj,d3a1,d3a2,d3s8,
+     .        d3atm,egap,et,maxiter,maxoptcycle,epot,grd,optlev,
+     .        .true.,fail)
+
+   !     call system('mv hessian.xtbtmp hessian 2>/dev/null') 
+
+end subroutine optts
diff --git a/src/axis_trafo.f90 b/src/axis_trafo.f90
index 32dd280ac..4d084e939 100644
--- a/src/axis_trafo.f90
+++ b/src/axis_trafo.f90
@@ -112,96 +112,128 @@ subroutine axis(numat,nat,xyz,aa,bb,cc)
     return
   end subroutine axis
 
-  subroutine axis2(numat,nat,xyz,aa,bb,cc,avmom,sumw)
-    use xtb_splitparam
-    implicit double precision (a-h,o-z)
-    dimension xyz(3,numat)
-    integer nat(numat)
 
-    PARAMETER (BOHR=0.52917726)
-    dimension t(6), rot(3), xyzmom(3), eig(3), evec(3,3)
-    dimension x(numat),y(numat),z(numat),coord(3,numat)
-    data t /6*0.d0/
-    !************************************************************************
-    !*     const1 =  10**40/(n*a*a)
-    !*               n = avergadro's number
-    !*               a = cm in an angstrom
-    !*               10**40 is to allow units to be 10**(-40)gram-cm**2
-    !*
-    !************************************************************************
-    const1 = 1.66053d0
-    !************************************************************************
-    !*
-    !*     const2 = conversion factor from angstrom-amu to cm**(-1)
-    !*
-    !*            = (planck's constant*n*10**16)/(8*pi*pi*c)
-    !*            = 6.62618*10**(-27)[erg-sec]*6.02205*10**23*10**16/
-    !*              (8*(3.1415926535)**2*2.997925*10**10[cm/sec])
-    !*
-    !************************************************************************
-    const2=16.8576522d0
-
-    sumw=1.d-20
-    sumwx=0.d0
-    sumwy=0.d0
-    sumwz=0.d0
 
-    coord(1:3,1:numat)=xyz(1:3,1:numat)*bohr
+subroutine axis2(n,xyz,aa,bb,cc,avmom,sumw)
+   
+   use xtb_splitparam, only : atmass
+   use xtb_mctc_convert, only : autoaa
+   
+   implicit double precision (a-h,o-z)
+   
+   !> number of atoms 
+   integer, intent(in) :: n
+   
+   !> cartesian coordinates
+   real(wp), intent(in) :: xyz(:,:)
+
+   !> rotational constants
+   real(wp), intent(out) :: aa,bb,cc
+
+   !> average moment of inertia
+   real(wp), intent(out) :: avmom
+
+   !> sum of atomic masses
+   real(wp), intent(out) :: sumw
+   
+   !> const1 =  10**40/(n*a*a)
+   !>            n = avergadro's number
+   !>            a = cm in an angstrom
+   !>            10**40 is to allow units to be 10**(-40)gram-cm**2
+   real(wp), parameter :: const1 = 1.66053_wp
+
+   !> const2 = conversion factor from angstrom-amu to cm**(-1)
+   !>        = (planck's constant*n*10**16)/(8*pi*pi*c)
+   !>        = 6.62618*10**(-27)[erg-sec]*6.02205*10**23*10**16/
+   !>         (8*(3.1415926535)**2*2.997925*10**10[cm/sec])
+   real(wp), parameter :: const2 = 16.8576522_wp
+
+   !> temporary variables
+   real(wp) :: xsum,eps,ams
+   
+   !> weighted sum of coordinates
+   real(wp) :: sumwx,sumwy,sumwz
+
+   !> loop variables
+   integer :: i
+
+   !> temporary arrays
+   real(wp) :: t(6), rot(3), xyzmom(3), eig(3), evec(3,3)
+   real(wp) :: x(n),y(n),z(n)
+
+   !> Cartesian coordinates in Bohr
+   real(wp) :: coord(3,n)  
+   
+   t(:)  = 0.0_wp 
+   sumw  = 0.0_wp
+   sumwx = 0.0_wp
+   sumwy = 0.0_wp
+   sumwz = 0.0_wp
+
+   ! convert Bohr to Angstrom ! 
+   coord(:,:) = xyz(:,:) * autoaa
+   
+   ! cma !
+   do i=1,n
+      sumw=sumw+atmass(i)
+      sumwx=sumwx+atmass(i)*coord(1,i)
+      sumwy=sumwy+atmass(i)*coord(2,i)
+      sumwz=sumwz+atmass(i)*coord(3,i)
+   enddo
+
+   sumwx=sumwx/sumw
+   sumwy=sumwy/sumw
+   sumwz=sumwz/sumw
+
+   do i=1,n
+      x(i)=coord(1,i)-sumwx
+      y(i)=coord(2,i)-sumwy
+      z(i)=coord(3,i)-sumwz
+   enddo
+
+   !************************************************************************
+   !*    matrix for moments of inertia is of form
+   !*
+   !*           |   y**2+z**2                         |
+   !*           |    -y*x       z**2+x**2             | -i =0
+   !*           |    -z*x        -z*y       x**2+y**2 |
+   !*
+   !************************************************************************
+   do i=1,6
+      t(i)=dble(i)*1.0d-10
+   enddo
+
+   do i=1,n
+      t(1)=t(1)+atmass(i)*(y(i)**2+z(i)**2)
+      t(2)=t(2)-atmass(i)*x(i)*y(i)
+      t(3)=t(3)+atmass(i)*(z(i)**2+x(i)**2)
+      t(4)=t(4)-atmass(i)*z(i)*x(i)
+      t(5)=t(5)-atmass(i)*y(i)*z(i)
+      t(6)=t(6)+atmass(i)*(x(i)**2+y(i)**2)
+   enddo
+
+   call rsp(t,3,3,eig,evec)
+   
+   do i=1,3
+
+      if(eig(i).lt.3.d-4) then
+         eig(i)=0.d0
+         rot(i)=0.d0
+      else
+         rot(i)=2.9979245d+4*const2/eig(i)
+      endif
 
-    do i=1,numat
-       sumw=sumw+atmass(i)
-       sumwx=sumwx+atmass(i)*coord(1,i)
-       sumwy=sumwy+atmass(i)*coord(2,i)
-       sumwz=sumwz+atmass(i)*coord(3,i)
-    enddo
+      xyzmom(i)=eig(i)*const1
 
-    sumwx=sumwx/sumw
-    sumwy=sumwy/sumw
-    sumwz=sumwz/sumw
-    f=1.0d0/bohr
-    do i=1,numat
-       x(i)=coord(1,i)-sumwx
-       y(i)=coord(2,i)-sumwy
-       z(i)=coord(3,i)-sumwz
-    enddo
+   enddo
 
-    !************************************************************************
-    !*    matrix for moments of inertia is of form
-    !*
-    !*           |   y**2+z**2                         |
-    !*           |    -y*x       z**2+x**2             | -i =0
-    !*           |    -z*x        -z*y       x**2+y**2 |
-    !*
-    !************************************************************************
-    do i=1,6
-       t(i)=dble(i)*1.0d-10
-    enddo
-    do i=1,numat
-       t(1)=t(1)+atmass(i)*(y(i)**2+z(i)**2)
-       t(2)=t(2)-atmass(i)*x(i)*y(i)
-       t(3)=t(3)+atmass(i)*(z(i)**2+x(i)**2)
-       t(4)=t(4)-atmass(i)*z(i)*x(i)
-       t(5)=t(5)-atmass(i)*y(i)*z(i)
-       t(6)=t(6)+atmass(i)*(x(i)**2+y(i)**2)
-    enddo
-    call rsp(t,3,3,eig,evec)
-    do i=1,3
-       if(eig(i).lt.3.d-4) then
-          eig(i)=0.d0
-          rot(i)=0.d0
-       else
-          rot(i)=2.9979245d+4*const2/eig(i)
-       endif
-       xyzmom(i)=eig(i)*const1
-    enddo
+   aa=rot(3)/2.9979245d+4
+   bb=rot(2)/2.9979245d+4
+   cc=rot(1)/2.9979245d+4
 
-    aa=rot(3)/2.9979245d+4
-    bb=rot(2)/2.9979245d+4
-    cc=rot(1)/2.9979245d+4
-    avmom=1.d-47*(xyzmom(1)+xyzmom(2)+xyzmom(3))/3.
+   avmom=1.d-47*(xyzmom(1)+xyzmom(2)+xyzmom(3))/3.
 
-    return
-  end subroutine axis2
+end subroutine axis2
 
   subroutine axisvec(numat,nat,xyz,aa,bb,cc,evec)
     use xtb_splitparam
diff --git a/src/geoopt_driver.f90 b/src/geoopt_driver.f90
index 55985c4e0..b401bfed4 100644
--- a/src/geoopt_driver.f90
+++ b/src/geoopt_driver.f90
@@ -18,66 +18,81 @@
 module xtb_geoopt
 contains
 
+!> wrapper for relaxation engines
+!> more info: https://xtb-docs.readthedocs.io/en/latest/optimization.html 
 subroutine geometry_optimization &
       &   (env,mol,wfn,calc,egap,et,maxiter,maxcycle_in,etot,g,sigma, &
       &    tight,pr,initial_sp,fail)
+
    use xtb_mctc_accuracy, only : wp
    use xtb_mctc_io, only : stdout
-
    use xtb_type_molecule
    use xtb_type_restart
    use xtb_type_calculator
    use xtb_type_data
-
    use xtb_optimizer
    use xtb_relaxation_engine
    use xtb_single
-
    use xtb_setparam
 
-   ! Declaration section
    implicit none
    
    character(len=*), parameter :: source = 'xtb_geoopt'
    
-   !> Dummy-argument list
+   !> instace of polymorphic calculatior
    class(TCalculator), intent(inout) :: calc
-      !! instance of calculatior
+   
+   !> calculation environment
    type(TEnvironment), intent(inout) :: env
-      !! calculation environment
+   
+   !> molecular data information
    type(TMolecule), intent(inout) :: mol
-      !! molecular information
+
+   !> wavefunction
    type(TRestart),intent(inout) :: wfn
-      !! wavefunction
+   
+   !> optimization level
    integer, intent(in)    :: tight
-      !! optimization level
+
+   !> max number of SCC cycles
    integer, intent(in)    :: maxiter
-      !! max number of SCC cycles
+   
+   !> max number of optimization cycles
    integer, intent(in)    :: maxcycle_in
-      !! max number of optimization cycles
+   
+   !> total energy
    real(wp),intent(inout) :: etot
-      !! total energy
+   
+   !> electronic temperature 
    real(wp),intent(in)    :: et
-      !! electronic temprature 
+   
+   !> HOMO-LUMO gap
    real(wp),intent(inout) :: egap
-      !! HOMO-LUMO gap
+   
+   !> gradients
    real(wp),intent(inout) :: g(3,mol%n)
-      !! gradients
+   
+   !> strain derivatives
    real(wp),intent(inout) :: sigma(3,3)
-      !! strain derivatives
+   
+   !> internal printlevel 
    logical, intent(in)    :: pr
-      !! printlevel 
+   
+   !> optimization convergence
    logical, intent(out)   :: fail
-      !! true->  optimization not converged
+   
+   !> perform initial single point 
    logical, intent(in)    :: initial_sp
-      !! true->  perform initial single point 
 
-   !> Local variables
    type(scc_results) :: res
    logical :: final_sp, exitRun
    integer :: printlevel
    integer :: ilog
 
+!----------------!
+! Initialization !
+!----------------!
+
    final_sp = pr
 
    if (pr) then
@@ -88,10 +103,9 @@ subroutine geometry_optimization &
       printlevel = 0
    endif
    
-   !> create optimization log file
+   ! create/open optimization log !
    if (.not.allocated(set%opt_logfile)) then
       call open_file(ilog,'xtbopt.log','w')
-      !! default
    else
       if (set%opt_logfile == '-') then
          ilog = stdout
@@ -102,36 +116,46 @@ subroutine geometry_optimization &
       endif
    endif
    
+   ! create ONIOM optimization logs for low & high methods ! 
    if (set%oniom_settings%logs) then
       call open_file(set%oniom_settings%ilog1,"low.inner_region.log",'w')
       call open_file(set%oniom_settings%ilog2,"high.inner_region.log",'w')
    endif
 
-   call mol%update
-      !! update interatomic and minimum image(periodic) distances 
+   call mol%update ! update interatomic and minimum image (periodic) distances 
+
+!-------------!
+! Calculation !
+!-------------!
 
    if (initial_sp)  call singlepoint &
          &(env,mol,wfn,calc, &
          & egap,et,maxiter,printlevel-1,.false.,.false.,1.0_wp,etot,g,sigma,res)
 
-   !> actual calculation
    select case(set%opt_engine)
-   case(p_engine_rf)
+   case(p_engine_rf) ! ANCopt !
       call ancopt &
          &(env,ilog,mol,wfn,calc, &
          & egap,et,maxiter,maxcycle_in,etot,g,sigma,tight,pr,fail)
-      final_sp = .true.
-         !! required since ANCopt might perform an untracked displacement
+      final_sp = .true. ! required since ANCopt might perform an untracked displacement 
+   
    case(p_engine_lbfgs)
-      call l_ancopt &
+      call l_ancopt & ! L-ANCopt !
          &(env,ilog,mol,wfn,calc, &
          & tight,maxcycle_in,etot,egap,g,sigma,printlevel,fail)
+   
    case(p_engine_inertial)
-      call fire &
+      call fire & ! FIRE !
          &(env,ilog,mol,wfn,calc, &
          & tight,maxcycle_in,etot,egap,g,sigma,printlevel,fail)
+   
    end select
-    
+  
+!-----------------!
+! Post-processing !
+!-----------------!
+
+   ! check convergence !
    if (pr) then
       if (fail) then
          call touch_file('NOT_CONVERGED')
@@ -141,14 +165,14 @@ subroutine geometry_optimization &
       endif
    end if
 
-   call env%check(exitRun)
-      !! check if any errors occur
+   call env%check(exitRun) ! error check 
 
    if (exitRun) then
       call env%rescue("Trying to recover from failed geometry optimization", source)
       fail = .true.
    end if
    
+   ! print fine details of optimized geometry !
    if (pr.and.set%pr_finalstruct) then
       write(env%unit,'(''================'')')
       write(env%unit,*) 'final structure:'
@@ -157,7 +181,7 @@ subroutine geometry_optimization &
    endif
    if (pr.and.set%pr_geosum) call geosum(mol%n,mol%at,mol%xyz)
    
-   !> usually final SP is performed for all three engines
+   ! final SP (usually for all engines) !
    if (final_sp) then
       if (pr) call generic_header(env%unit,'Final Singlepoint',49,10)
       call singlepoint &
@@ -165,9 +189,10 @@ subroutine geometry_optimization &
          & egap,et,maxiter,printlevel,.false.,.false.,1.0_wp,etot,g,sigma,res)
    endif
    
-   if (ilog .ne.stdout) call close_file(ilog)
-      !! close log file if it is not printed out on stdout
+   ! close log file !
+   if (ilog.ne.stdout) call close_file(ilog)
    
+   ! close ONIOM optlogs !
    if (set%oniom_settings%logs) then
       call close_file(set%oniom_settings%ilog1)
       call close_file(set%oniom_settings%ilog2)
diff --git a/src/main/property.F90 b/src/main/property.F90
index d7806d8fc..578c71453 100644
--- a/src/main/property.F90
+++ b/src/main/property.F90
@@ -1059,7 +1059,7 @@ subroutine print_thermo(iunit,nat,nvib_in,at,xyz,freq,etot,htot,gtot,nimag,pr,zp
    nvib=0
    nimag=0
 
-   call axis2(nat,at,xyz,aa,bb,cc,avmom,wt)
+   call axis2(nat,xyz,aa,bb,cc,avmom,wt)
 
    nvib_theo=3*nat-6
    if(cc.lt.1.d-10) linear=.true.
diff --git a/src/model_hessian.f90 b/src/model_hessian.f90
index bf09d82b3..af87dffc3 100644
--- a/src/model_hessian.f90
+++ b/src/model_hessian.f90
@@ -2081,14 +2081,15 @@ end subroutine mh_eeq
 
 end module xtb_modelhessian
 
-      subroutine ddvopt(Cart,nAtoms,Hess,iANr,s6)
-      Implicit Integer(i-n)
-      Implicit Real*8 (a-h, o-z)
+subroutine ddvopt(Cart,nAtoms,Hess,iANr,s6)
+   
+   implicit integer(i-n)
+   implicit real*8 (a-h, o-z)
 ! include "common/real.inc" (molpro 2002.6)
-      Real*8 Zero, One, Two, Three, Four, Five, Six, Seven, &
+   real*8 :: Zero, One, Two, Three, Four, Five, Six, Seven, &
      &       Eight, RNine, Ten, Half, Pi, SqrtP2, TwoP34, &
      &       TwoP54, One2C2
-      Parameter(Zero =0.0D0, One  =1.0D0, Two=2.0D0, Three=3.0D0, &
+   parameter :: (Zero =0.0D0, One  =1.0D0, Two=2.0D0, Three=3.0D0, &
      &          Four =4.0D0, Five =5.0D0, Six=6.0D0, Seven=7.0D0, &
      &          Eight=8.0D0, rNine=9.0D0, Ten=1.0D1, Half=0.5D0, &
      &          Pi    =3.141592653589793D0, &
@@ -2098,16 +2099,16 @@ subroutine ddvopt(Cart,nAtoms,Hess,iANr,s6)
      &          One2C2=0.2662567690426443D-04)
 ! end: common/real.inc
 
-      Real*8 Cart(3,nAtoms),rij(3),rjk(3),rkl(3), &
+   real*8 :: Cart(3,nAtoms),rij(3),rjk(3),rkl(3), &
      &       Hess((3*nAtoms)*(3*nAtoms+1)/2),si(3),sj(3),sk(3), &
      &       sl(3),sm(3),x(2),y(2),z(2), &
      &       xyz(3,4), C(3,4), Dum(3,4,3,4)
-      Integer   iANr(nAtoms)
+   integer :: iANr(nAtoms)
 
-      logical rcutoff
+   logical :: rcutoff
 
 ! include  "common/ddvdt.inc" (molpro 2002.6)
-      Real*8 rAV(3,3), aAV(3,3), &
+   real*8 :: rAV(3,3), aAV(3,3), &
      &       B_Str(6), A_Bend(2), A_Trsn(2), A_StrH(2), &
      &       rkr, rkf, A_Str, RF_Const, &
      &       wthr
@@ -2130,10 +2131,10 @@ subroutine ddvopt(Cart,nAtoms,Hess,iANr,s6)
 ! end: "common/ddvdt.inc"
 
 !cc VDWx-Parameters (Grimme) used for vdw-correction of model hessian
-      real*8 alphavdw, damp, c6(100), c6k, c6l, c66, vander(100), &
+   real*8 :: alphavdw, damp, c6(100), c6k, c6l, c66, vander(100), &
      &   vdw(3,3), dr(3)
-      integer kxyz, lxyz
-      data vander &
+   integer kxyz, lxyz
+   data vander &
 ! H, He
      &     /0.91d0,0.92d0, &
 ! Li-Ne
@@ -2650,7 +2651,7 @@ subroutine ddvopt(Cart,nAtoms,Hess,iANr,s6)
 444     Continue
       End Do               ! jAtom
       Return
-      End
+   end subroutine
 
       subroutine gff_ddvopt(Cart,nAtoms,Hess,at,s6,param,topo)
       use xtb_gfnff_data, only : TGFFData
diff --git a/src/optimizer.f90 b/src/optimizer.f90
index 691f3d033..aa3e5ac2a 100644
--- a/src/optimizer.f90
+++ b/src/optimizer.f90
@@ -25,6 +25,7 @@ module xtb_optimizer
    use xtb_david2
    implicit none
 
+   !> time profiling
    logical,private,parameter :: profile = .true.
 
    type :: convergence_log
@@ -42,6 +43,7 @@ module xtb_optimizer
 
 contains
 
+!> construct optimizer settings from optimization level
 subroutine get_optthr(n,olev,ethr,gthr,maxcycle,acc)
    use xtb_setparam
    implicit none
@@ -51,66 +53,74 @@ subroutine get_optthr(n,olev,ethr,gthr,maxcycle,acc)
    real(wp),intent(out) :: gthr
    integer, intent(out) :: maxcycle
    real(wp),intent(out) :: acc
+   
    select case(olev)
-! very approximate = crude
+   ! very approximate = crude !
    case(p_olev_crude)
       ethr   = 5.d-4
       gthr   = 1.d-2
       maxcycle=n
       acc=3.00d0
-! approximate = sloopy
+   
+   ! approximate = sloopy !
    case(p_olev_sloppy)
       ethr   = 1.d-4
       gthr   = 6.d-3
       maxcycle=n
       acc=3.00d0
-! loose
+   
+   ! loose !
    case(p_olev_loose)
       ethr   = 5.d-5
       gthr   = 4.d-3
       maxcycle=n*2
       acc=2.00d0
-!  for DCOSMO-RS opts with TM i.e. between loose and normal, keyword "lax"
+
+   ! for DCOSMO-RS opts with TM i.e. between loose and normal !
    case(p_olev_lax)
       ethr   = 2.d-5
       gthr   = 2.5d-3
       maxcycle=n*2
       acc=2.00d0
-!  normal
+   
+   ! normal !
    case default
       ethr  = 5.d-6
       gthr  = 1.d-3
       maxcycle=n*3
       acc=1.0d0
-! tight
+   
+   ! tight !
    case(p_olev_tight)
       ethr   = 1.d-6
       gthr   = 8.d-4
       maxcycle=n*5
       acc=0.20d0
-! very tight
+
+   ! very tight !
    case(p_olev_vtight)
       ethr   = 1.d-7
       gthr   = 2.d-4
       maxcycle=n*20
       acc=0.05d0
-! extreme
+
+   ! extreme !
    case(p_olev_extreme)
       ethr   = 5.d-8
       gthr   = 5.d-5
       maxcycle=n*20
       acc=0.01d0
    end select
+   
    maxcycle=min(maxcycle,10000)
    maxcycle=max(maxcycle,200)
 
 end subroutine get_optthr
 
-!----------------------------------------
-! Approximate Normal Coordinate Optimizer
-!----------------------------------------
+!> Approximate Normal Coordinate rational function optimizer 
 subroutine ancopt(env,ilog,mol,chk,calc, &
       &           egap,et,maxiter,maxcycle_in,etot,g,sigma,tight,pr,fail)
+   
    use xtb_mctc_convert
    use xtb_mctc_la
 
@@ -132,67 +142,143 @@ subroutine ancopt(env,ilog,mol,chk,calc, &
    use xtb_lsrmsd
 
    implicit none
-
+   
+   !> traceback for error handling 
    character(len=*), parameter :: source = "optimizer_ancopt"
-      !! source of errors in the main program unit
+   
+   !> calculation environment
    type(TEnvironment), intent(inout) :: env
-      !! calculation environment
+   
+   !> molecular structure data
    type(TMolecule), intent(inout) :: mol
-      !! molecular structure data
+   
+   !> optimization level
    integer, intent(in)    :: tight
-      !! optimization level
+   
+   !> max number of SCC cycles
    integer, intent(in)    :: maxiter
-      !! max SCC cycles
+   
+   !> max number of optimization cycles
    integer, intent(in)    :: maxcycle_in
-      !! max GEOOPT cycles
+   
+   !> wrapper for changing info during SCC
    type(TRestart),intent(inout) :: chk
-      !! wrapper for changing info during SCC
+
+   !> polymorphic calculator instance
    class(TCalculator), intent(inout) :: calc
-      !! calculator instance
+   
+   !> electronic energy
    real(wp) :: eel
-      !! electronic energy
+
+   !> total energy
    real(wp),intent(inout) :: etot
-      !! total energy
+   
+   !> electronic temperature
    real(wp),intent(in)    :: et
-      !! electronic temperature
+   
+   !> HOMO-LUMO gap
    real(wp),intent(inout) :: egap
-      !! HOMO-LUMO gap
+   
+   !> gradients
    real(wp),intent(inout) :: g(3,mol%n)
-      !! gradients
+   
+   !> strain derivatives
    real(wp),intent(inout) :: sigma(3,3)
-      !! strain derivatives
+   
+   !> printlevel
    logical, intent(in)    :: pr
-      !! if printed
+   
+   !> optimization failure
    logical, intent(out)   :: fail
-      !! if failed
+
+!-----------------!   
+! local variables !
+!-----------------!   
    
-   !> local variables
    type(TMolecule) :: molopt
    type(scc_results) :: res
    type(tb_anc) :: anc
    type(tb_timer) :: timer
-   real(wp) :: step,amu2au,au2cm,dumi,dumj,damp,hlow,edum,s6,thr,aaa,bbb
-   real(wp) :: maxdispl,gthr,ethr,hmax,energy,acc,rij(3),t1,t0,w1,w0,ccc
-   integer  :: n3,i,j,k,l,jjj,ic,jc,ia,ja,ii,jj,info,lwork,nat3,liwork
-   integer  :: nvar,iter,nread,maxcycle,maxmicro,itry,maxopt,iupdat,iii
+
+   !> maximum coordinate displacement
+   real(wp) :: maxdispl
+
+   !> lowest value for force constant
+   real(wp) :: hlow
+
+   !> highest value for force constant
+   real(wp) :: hmax 
+
+   !> dispersion scaling
+   real(wp) :: s6
+
+   !> total energy from initial single point callculation
+   real(wp) :: estart
+
+   !> energy & gradient convergence thresholds
+   real(wp) :: ethr, gthr
+   
+   
+   !> number of modes followed
+   integer :: modef
+   
+   !> max number of opt cycles
+   integer :: maxopt
+
+   !> max number of opt cycles before generation of new ANC
+   integer :: maxmicro
+   
+   !> algorithm for updating Hessian  
+   integer :: iupdat ! 0 = BFGS, 1 = Powell
+   
+   !> current iteration 
+   integer :: iter
+
+   !> number of atomic coordinates
+   integer :: nat3
+
+   !> deegrees of freedom
+   integer :: nvar
+
+   !> work array size
+   integer :: lwork, liwork
+
+   real(wp) :: step,amu2au,au2cm,dumi,dumj,damp,edum,thr,aaa,bbb
+   real(wp) :: energy,acc,rij(3),t1,t0,w1,w0,ccc
+
+   integer  :: n3,i,j,k,l,jjj,ic,jc,ia,ja,ii,jj,info
+   integer  :: nread,itry,iii
    integer  :: id,ihess,error
    integer, intent(in)  :: ilog
    integer, external    :: lin
+
+   !> Hessian matrix
    real(wp),allocatable :: h (:,:)
+
    real(wp),allocatable :: b (:,:)
+   real(wp),allocatable :: pmode(:,:)
+   real(wp),allocatable :: grmsd(:,:)
+
+   !> force constants
    real(wp),allocatable :: fc(:)
+
+   !> eigenvalues
    real(wp),allocatable :: eig(:)
+
    real(wp),allocatable :: aux(:)
    real(wp),allocatable :: hess(:)
    integer, allocatable :: iwork(:)
    integer, allocatable :: totsym(:)
-   real(wp),allocatable :: pmode(:,:)
-   real(wp),allocatable :: grmsd(:,:)
    type(convergence_log), allocatable :: avconv
+   
    real(wp) :: U(3,3), x_center(3), y_center(3), rmsdval
-   integer :: modef
-   logical :: restart,ex,converged,linear
-   real(wp) :: estart,esave
+   real(wp) :: esave
+   logical :: restart,ex,converged
+   
+   !>  if linear molecule
+   logical :: linear
+   
+   !> formatting strings for output 
    character(len=*),parameter :: scifmt = &
       '(10x,":",3x,a,e22.7,1x,a,1x,":")'
    character(len=*),parameter :: dblfmt = &
@@ -202,42 +288,43 @@ subroutine ancopt(env,ilog,mol,chk,calc, &
    character(len=*),parameter :: chrfmt = &
       '(10x,":",3x,a,a18,      10x,":")'
    
-   ! Print ANCopt header !
+   ! print ANCopt header !
    call ancopt_header(env%unit,set%veryverbose)
    
-   if(mol%n.eq.1) return
-      !! do not optimize for 1 molecule
+   if(mol%n.eq.1) return ! skip optimization for 1 atom 
+
+   ! performance profiling timer !
    if (profile) call timer%new(8,.false.)
    if (profile) call timer%measure(1,'optimizer setup')
-
-!  defaults
-   fail =.false.
-   modef=0
-   hmax =  5.0_wp
-   maxdispl=set%optset%maxdispl_opt
-   hlow = set%optset%hlow_opt!0.01 in ancopt, 0.002 too small
-   s6   = set%mhset%s6  !slightly better than 30 for various proteins
-! initial number of steps before new ANC are made by model Hessian
-! increased during opt.
-   maxmicro=set%optset%micro_opt
+   
+   ! defaults !
+   iter = 0
+   fail  = .false.
+   modef = 0
+   iupdat= 0 
+   hmax  = 5.0_wp
+   nat3 = 3 * mol%n
+   maxdispl = set%optset%maxdispl_opt  ! def: 1.0
+   hlow = set%optset%hlow_opt          ! def: 0.01 
+   s6   = set%mhset%s6                 ! def: 20.0
+   maxmicro=set%optset%micro_opt       ! def: 20 
    estart = etot
-
-   iupdat=0 !0=BFGS, 1=Powell
-
+   call get_optthr(mol%n,tight,ethr,gthr,maxopt,acc)
+   
+   ! if provided by user !
+   if(maxcycle_in.gt.0)then
+      maxopt=maxcycle_in
+   endif
+   if(maxopt.lt.maxmicro) maxmicro=maxopt
+   
+   ! use Powell update if TS optimization (-> not implemeted) ! 
    if(set%tsopt)then
       hlow=max(hlow,0.250d0)
       iupdat=1
    endif
-
-   call get_optthr(mol%n,tight,ethr,gthr,maxcycle,acc)
-
-   if(maxcycle_in.le.0)then
-      maxopt=maxcycle
-   else
-      maxopt=maxcycle_in
-   endif
-   if(maxopt.lt.maxmicro) maxmicro=maxopt
-   if (set%optset%average_conv) then
+   
+   ! energy and gradient averaging !
+   if (set%optset%average_conv) then ! default: .false.
       select type(calc)
       class is(TTMCalculator)
          avconv = load_turbomole_log(maxopt)
@@ -250,22 +337,23 @@ subroutine ancopt(env,ilog,mol,chk,calc, &
       end select
    end if
 
-   call axis2(mol%n,mol%at,mol%xyz,aaa,bbb,ccc,dumi,dumj)
-
-   !call open_file(ilog,'xtbopt.log','w')
-   iter = 0
-   nat3 = 3 * mol%n
-   nvar = nat3 - 6
-   linear = .false.
-   if(ccc.lt.1.d-10) then
+   ! determine if linear molecule !
+   call axis2(mol%n,mol%xyz,aaa,bbb,ccc,dumi,dumj)
+   if (ccc.lt.1.d-10) then
       linear = .true.
       nvar = nat3 - 5
+   else
+      linear = .false.
+      nvar = nat3 - 6
    endif
-   if(fixset%n.gt.0) then ! exact fixing
-      nvar=nat3-3*fixset%n-3
+
+   ! exact fixing case ! 
+   if(fixset%n.gt.0) then 
+      nvar = nat3 - 3*fixset%n - 3
       if(nvar.le.0) nvar=1
    endif
 
+   ! adjust if restrated !
    call open_binary(id,'.xtbtmpmode','r')
    if(id.ne.-1)then
       read (id) modef
@@ -277,43 +365,52 @@ subroutine ancopt(env,ilog,mol,chk,calc, &
       allocate(pmode(nat3,1)) ! dummy allocated
    endif
 
+   ! print ANCopt settings !
    if(pr)then
       write(env%unit,'(/,10x,51("."))')
       write(env%unit,'(10x,":",22x,a,22x,":")') "SETUP"
       write(env%unit,'(10x,":",49("."),":")')
-      write(env%unit,chrfmt) "optimization level",int2optlevel(tight)
-      write(env%unit,intfmt) "max. optcycles    ",maxopt
-      write(env%unit,intfmt) "ANC micro-cycles  ",maxmicro
-      write(env%unit,intfmt) "degrees of freedom",nvar
+      write(env%unit,chrfmt) "optimization level", int2optlevel(tight)
+      write(env%unit,intfmt) "max. optcycles    ", maxopt
+      write(env%unit,intfmt) "ANC micro-cycles  ", maxmicro
+      write(env%unit,intfmt) "degrees of freedom", nvar
+      
       if (modef>0) then
-      write(env%unit,intfmt) "# mode follow     ",modef
+         write(env%unit,intfmt) "# mode follow     ", modef
       endif
+      
       write(env%unit,'(10x,":",49("."),":")')
+      
       if (set%optset%exact_rf) then
-      write(env%unit,chrfmt) "RF solver         ","spevx"
+         write(env%unit,chrfmt) "RF solver         ", "spevx"
       else
-      write(env%unit,chrfmt) "RF solver         ","davidson"
+         write(env%unit,chrfmt) "RF solver         ", "davidson"
       endif
-      write(env%unit,chrfmt) "write xtbopt.log  ",bool2string(ilog.ne.-1)
+      
+      write(env%unit,chrfmt) "write xtbopt.log  ", bool2string(ilog.ne.-1)
+      
       if (linear) then
-      write(env%unit,chrfmt) "linear (good luck)",bool2string(linear)
+         write(env%unit,chrfmt) "linear (good luck)", bool2string(linear)
       else
-      write(env%unit,chrfmt) "linear?           ",bool2string(linear)
+         write(env%unit,chrfmt) "linear?           ", bool2string(linear)
       endif
-      write(env%unit,scifmt) "energy convergence",ethr,    "Eh  "
-      write(env%unit,scifmt) "grad. convergence ",gthr,    "Eh/α"
-      write(env%unit,dblfmt) "maxmium RF displ. ",maxdispl,"    "
-      write(env%unit,scifmt) "Hlow (freq-cutoff)",hlow,    "    "
-      write(env%unit,dblfmt) "Hmax (freq-cutoff)",hmax,    "    "
-      write(env%unit,dblfmt) "S6 in model hess. ",s6,      "    "
+      
+      write(env%unit,scifmt) "energy convergence", ethr,    "Eh  "
+      write(env%unit,scifmt) "grad. convergence ", gthr,    "Eh/α"
+      write(env%unit,dblfmt) "maxmium RF displ. ", maxdispl,"    "
+      write(env%unit,scifmt) "Hlow (freq-cutoff)", hlow,    "    "
+      write(env%unit,dblfmt) "Hmax (freq-cutoff)", hmax,    "    "
+      write(env%unit,dblfmt) "S6 in model hess. ", s6,      "    "
       write(env%unit,'(10x,51("."))')
    endif
 
+   ! work arrays !
    lwork  = 1 + 6*nat3 + 2*nat3**2
    liwork = 8 * nat3
 
    allocate(h(nat3,nat3),fc(nat3*(nat3+1)/2),eig(nat3))
 
+   ! read in Hessian from file !
    if (set%mhset%model == p_modh_read) then
       call open_file(ihess, 'hessian', 'r')
       if (ihess == -1) then
@@ -332,39 +429,46 @@ subroutine ancopt(env,ilog,mol,chk,calc, &
       ex = .false.
    endif
 
-   call anc%allocate(mol%n,nvar,hlow,hmax)
-
-   molopt = mol
-
-   if (profile) call timer%measure(1)
+   call anc%allocate(mol%n,nvar,hlow,hmax) ! allocate ANC
+   molopt = mol ! copy molecular information
+   if (profile) call timer%measure(1) ! start opt timer
 
 ! ======================================================================
    ANC_microiter: do
 ! ======================================================================
 
-   if (profile) call timer%measure(2,'model hessian')
+   if (profile) call timer%measure(2,'model hessian') ! start timer for Hessian
+   
+   ! initial guess for Hessian !
    if (.not.ex)then ! normal case
-     if(pr)write(env%unit,'(/,''generating ANC from model Hessian ...'')')
-     call modhes(env, calc, set%mhset, molopt%n, molopt%xyz, molopt%at, fc, pr)   ! WBO (array wb) not used in present version
-     call env%check(fail)
-     if (fail) then
-        call env%error("Calculation of model hessian failed", source)
-        return
-     end if
-     !call qpothess(molopt%n,fc,molopt%xyz)
-     thr=1.d-11
-   else
-     if(pr)write(env%unit,'(/,''generating ANC from read Hessian ...'')')
-     k=0
-     do i=1,nat3
-        do j=1,i
-         k=k+1
-         fc(k)=h(j,i)
-        enddo
-     enddo
-     thr=1.d-10
+      if (pr) &
+         &  write(env%unit,'(/,''generating ANC from model Hessian ...'')')
+
+      call modhes(env, calc, set%mhset, molopt%n, molopt%xyz, molopt%at, fc, pr)   ! WBO (array wb) not used in present version
+      
+      call env%check(fail)
+     
+      if (fail) then
+         call env%error("Calculation of model hessian failed", source)
+         return
+      end if
+      !call qpothess(molopt%n,fc,molopt%xyz)
+      thr=1.d-11
+
+   else ! read in Hessian from file 
+      if(pr)write(env%unit,'(/,''generating ANC from read Hessian ...'')')
+      k=0
+      do i=1,nat3
+         do j=1,i
+            k=k+1
+            fc(k)=h(j,i)
+         enddo
+      enddo
+      thr=1.d-10
    endif
 
+   print*,fc
+   stop
    if(modef.eq.0)then
       if(fixset%n.gt.0)then
          call trproj(molopt%n,nat3,molopt%xyz,fc,.false., -1  ,pmode,1)     ! exact fixing
@@ -375,8 +479,10 @@ subroutine ancopt(env,ilog,mol,chk,calc, &
    else
       call trproj(molopt%n,nat3,molopt%xyz,fc,.false.,modef,pmode,modef) ! NMF
    endif
+   
    if (profile) call timer%measure(2)
 
+   stop
    if (profile) call timer%measure(3,'ANC generation')
    ! this is completely useless, we blow up the Hessian, just to pack it again...
    k=0
@@ -388,7 +494,7 @@ subroutine ancopt(env,ilog,mol,chk,calc, &
       enddo
    enddo
 
-!  initialize hessian for opt.
+   ! initialize hessian for opt. !
    call anc%new(env%unit,molopt%xyz,h,pr,linear)
 
    if (profile) call timer%measure(3)
@@ -665,9 +771,9 @@ subroutine relax(env,iter,mol,anc,restart,maxcycle,maxdispl,ethr,gthr, &
    if(ii.gt.1)then
 ! hessian update
       if(iupdat.eq.0)then
-      call bfgs  (anc%nvar,gnorm,gint,gold,displ,anc%hess)
+         call bfgs  (anc%nvar,gnorm,gint,gold,displ,anc%hess)
       else
-      call powell(anc%nvar,gnorm,gint,gold,displ,anc%hess)
+         call powell(anc%nvar,gnorm,gint,gold,displ,anc%hess)
       endif
    endif
    if (profile) call timer%measure(7)
@@ -758,6 +864,7 @@ subroutine relax(env,iter,mol,anc,restart,maxcycle,maxdispl,ethr,gthr, &
    restart=.true.
    etot=energy
    call anc%get_cartesian(mol%xyz)
+
 end subroutine relax
 
 pure subroutine solver_ssyevx(n,thr,A,U,e,fail)
@@ -991,6 +1098,7 @@ subroutine prdispl(nvar,displ)
 
 end subroutine prdispl
 
+!> generate model Hessian
 subroutine modhes(env, calc, modh, natoms, xyz, chg, Hess, pr)
    use xtb_type_setvar
    use xtb_modelhessian
@@ -1016,21 +1124,22 @@ subroutine modhes(env, calc, modh, natoms, xyz, chg, Hess, pr)
    type(modhess_setvar),intent(in) :: modh
    logical, intent(in)  :: pr
 
-!  Other variables
+   !> other variables
    integer  :: i
    integer  :: nhess
    integer, intent(in)  :: natoms
    real(wp),intent(in)  :: xyz(3,natoms)
-   real(wp),intent(out) :: hess((natoms*3)*((natoms*3)+1)/2)
+   
+   !> model hessian
+   real(wp),intent(out) :: Hess((natoms*3)*((natoms*3)+1)/2)
    integer, intent(in)  :: chg(natoms)
 
-!  initialize
-   nhess=3*natoms
-   Hess=0.d0
+   ! initialize !
+   Hess=0.0_wp
 
    select type(calc)
-   class default
-      select case(modh%model)
+   class default ! all calculator cases except GFN-FF
+      select case(modh%model) 
       case default
          call env%error("internal error in model hessian!", source)
          return
@@ -1047,7 +1156,7 @@ subroutine modhes(env, calc, modh, natoms, xyz, chg, Hess, pr)
         if (pr) write(env%unit,'(a)') "Using Swart-Hessian"
         call mh_swart(xyz, natoms, Hess, chg, modh)
       end select
-   type is(TGFFCalculator)
+   type is(TGFFCalculator) ! GFN-FF case
       select case(modh%model)
       case default
          call env%error("internal error in model hessian!", source)
diff --git a/src/setparam.f90 b/src/setparam.f90
index 993cc2c65..0c5b245a3 100644
--- a/src/setparam.f90
+++ b/src/setparam.f90
@@ -223,17 +223,16 @@ module xtb_setparam
    character(len=:), allocatable :: opt_outfile
    character(len=:), allocatable :: opt_logfile
    integer, allocatable :: opt_engine
+
+   !> ANCopt settings
    type(ancopt_setvar) :: optset = ancopt_setvar (&
       optlev = p_olev_normal, &
-!  number of opt. cycles before new ANC are made
-      micro_opt = 20, &
-!  total number of opt. cycles, 0 means automatically determined
+      micro_opt = 20, &  ! increased during opt.
       maxoptcycle = 0, & ! det. in ancopt routine if not read in
-!  maximum coordinate displacement in ancopt
       maxdispl_opt = 1.000_wp, &
-!  lowest force constant in ANC generation (should be > 0.005)
-      hlow_opt = 0.010_wp, &
+      hlow_opt = 0.010_wp, & ! 0.002 is too small
       average_conv = .false.)
+   
    type(modhess_setvar) :: mhset = modhess_setvar (&
       model = p_modh_old, &
 !  force constants for stretch, bend and torsion
diff --git a/src/splitparam.f90 b/src/splitparam.f90
index de34d1752..b515421fc 100644
--- a/src/splitparam.f90
+++ b/src/splitparam.f90
@@ -33,7 +33,9 @@ module xtb_splitparam
    real(wp) :: rcma = 0.0_wp
    real(wp) :: massf1 = 0.0_wp
    real(wp) :: massf2 = 0.0_wp
-   real(wp),allocatable :: atmass(:)
+   
+   !> atomic masses
+   real(wp), allocatable :: atmass(:)
 
    integer  :: maxfrag = 0
 
diff --git a/src/type/anc.f90 b/src/type/anc.f90
index e50652a85..ffc1ba05d 100644
--- a/src/type/anc.f90
+++ b/src/type/anc.f90
@@ -25,9 +25,9 @@ module xtb_type_anc
    private
 
    type tb_anc
-      integer  :: n    !< number of atoms
-      integer  :: n3   !< dimension of hessian
-      integer  :: nvar !< actual dimension
+      integer  :: n    ! number of atoms
+      integer  :: n3   ! dimension of hessian
+      integer  :: nvar ! actual dimension
       real(wp) :: hlow
       real(wp) :: hmax
       real(wp),allocatable :: hess(:)
diff --git a/src/type/setvar.f90 b/src/type/setvar.f90
index 4b8501847..385192cef 100644
--- a/src/type/setvar.f90
+++ b/src/type/setvar.f90
@@ -70,39 +70,51 @@ module xtb_type_setvar
       real(wp) :: broydamp = 0.40_wp
    end type scc_setvar
 
-!! ------------------------------------------------------------------------
-!  approximate normal coordinate rational function optimizer
-!! ------------------------------------------------------------------------
+   !>  approximate normal coordinate rational function optimizer 
    type :: ancopt_setvar
-!     default optimization level
-!     crude = -3,     sloppy = -2,      loose = -1,      normal = 0,
-!     tight = 1,      verytight = 2,    extreme = 3
+      
+      !> default optimization level
+      !> crude = -3,     sloppy = -2,      loose = -1,      normal = 0,
+      !> tight = 1,      verytight = 2,    extreme = 3
       integer  :: optlev = 0
-!     number of opt. cycles before new ANC are made
+      
+      !> number of opt. cycles before new ANC are made by model Hessian
       integer  :: micro_opt = 0
-!     total number of opt. cycles, 0 means automatically determined
-      integer  :: maxoptcycle = 0 ! det. in ancopt routine if not read in
-!     maximum coordinate displacement in ancopt
+
+      !> total number of opt. cycles, 0 means automatically determined
+      integer  :: maxoptcycle = 0 
+      
+      !> maximum coordinate displacement in ancopt
       real(wp) :: maxdispl_opt = 0.0_wp
-!     lowest force constant in ANC generation (should be > 0.005)
+      
+      !> lowest force constant in ANC generation (should be > 0.005)
       real(wp) :: hlow_opt = 0.0_wp
-      logical  :: exact_rf = .false.
+      
+      logical :: exact_rf = .false.
+
+      !> average energy and gradient before checking for convergence 
+      !> to accelerate numerically noisy potential energy surfaces
       logical :: average_conv = .false.
+
    end type ancopt_setvar
 
    type modhess_setvar
       integer  :: model = 0
-!     force constants for stretch, bend and torsion
+      
+      !> cutoff for constructing internal coordinates
+      real(wp) :: rcut = 0.0_wp
+      
+      !> dispersion scaling in ANC generation
+      real(wp) :: s6 = 0.0_wp
+   
+      !> force constants for stretch, bend and torsion
       real(wp) :: kr = 0.0_wp
       real(wp) :: kf = 0.0_wp
       real(wp) :: kt = 0.0_wp
       real(wp) :: ko = 0.0_wp
       real(wp) :: kd = 0.0_wp
       real(wp) :: kq = 0.0_wp
-!     cutoff for constructing internal coordinates
-      real(wp) :: rcut = 0.0_wp
-!     dispersion scaling in ANC generation
-      real(wp) :: s6 = 0.0_wp
+   
    end type modhess_setvar
 
 !! ------------------------------------------------------------------------
diff --git a/test/unit/test_thermo.f90 b/test/unit/test_thermo.f90
index f1b676f5f..8da8499af 100644
--- a/test/unit/test_thermo.f90
+++ b/test/unit/test_thermo.f90
@@ -94,7 +94,7 @@ subroutine test_axis(error)
    call check(error, rot1(2), .226266337664493_wp, thr=thr2)
    call check(error, rot1(3), 7.01216792608729_wp, thr=thr2)
 
-   call axis2(mol%n, mol%at, mol%xyz, rot2(1), rot2(2), rot2(3), avmom2, mass2)
+   call axis2(mol%n,  mol%xyz, rot2(1), rot2(2), rot2(3), avmom2, mass2)
 
    call check(error, rot2(1), .226251131473004_wp, thr=thr2)
    call check(error, rot2(2), .226266337664493_wp, thr=thr2)
@@ -128,7 +128,7 @@ subroutine test_axis(error)
    call check(error, rot1(2), .19263614502269_wp, thr=thr2)
    call check(error, rot1(3), 4.7581644454539_wp, thr=thr2)
 
-   call axis2(mol%n, mol%at, mol%xyz, rot2(1), rot2(2), rot2(3), avmom2, mass2)
+   call axis2(mol%n, mol%xyz, rot2(1), rot2(2), rot2(3), avmom2, mass2)
 
    call check(error, rot2(1), .19017218374861_wp, thr=thr2)
    call check(error, rot2(2), .19263614502269_wp, thr=thr2)