Merge pull request #648 from votca/RPA_correction_refactor

refactoring energy corrections outside qpmin:qpmax for RPA

CHANGELOG.rst

@@ -5,8 +5,10 @@ Version 2022-dev
 ================
 
 -  Updated coordinate precision (#638)
+-  Refactored energy corrections in RPA outside QPs (#577)
 -  Made SetupCptTable static (#650)
 
+
 Version 2021-rc.2 (released XX.01.21)
 =====================================
 

include/votca/xtp/rpa.h

@@ -1,5 +1,5 @@
 /*
- *            Copyright 2009-2020 The VOTCA Development Team
+ *            Copyright 2009-2021 The VOTCA Development Team
  *                       (http://www.votca.org)
  *
  *      Licensed under the Apache License, Version 2.0 (the "License")
@@ -92,6 +92,12 @@ class RPA {
   Eigen::MatrixXd Calculate_H2p_ApB() const;
   Eigen::SelfAdjointEigenSolver<Eigen::MatrixXd> Diagonalize_H2p_C(
       const Eigen::MatrixXd& C) const;
+
+  void ShiftUncorrectedEnergies(const Eigen::VectorXd& dftenergies, Index qpmin,
+                                Index gwsize);
+
+  double getMaxCorrection(const Eigen::VectorXd& dftenergies, Index min,
+                          Index max) const;
 };
 
 }  // namespace xtp

src/libxtp/gwbse/rpa.cc

@@ -1,5 +1,5 @@
 /*
- *            Copyright 2009-2020 The VOTCA Development Team
+ *            Copyright 2009-2021 The VOTCA Development Team
  *                       (http://www.votca.org)
  *
  *      Licensed under the Apache License, Version 2.0 (the "License")
@@ -33,26 +33,41 @@ void RPA::UpdateRPAInputEnergies(const Eigen::VectorXd& dftenergies,
   Index rpatotal = _rpamax - _rpamin + 1;
   _energies = dftenergies.segment(_rpamin, rpatotal);
   Index gwsize = Index(gwaenergies.size());
-  Index lumo = _homo + 1;
 
-  Index qpmax = qpmin + gwsize - 1;
   _energies.segment(qpmin - _rpamin, gwsize) = gwaenergies;
 
-  Eigen::VectorXd corrections_occ =
-      _energies.segment(qpmin - _rpamin, lumo - qpmin) -
-      dftenergies.segment(qpmin - _rpamin, lumo - qpmin);
-  Eigen::VectorXd corrections_virt =
-      _energies.segment(lumo - qpmin, gwsize - (lumo - qpmin)) -
-      dftenergies.segment(lumo - qpmin, gwsize - (lumo - qpmin));
-  double max_correction_occ = (corrections_occ.cwiseAbs()).maxCoeff();
-  double max_correction_virt = (corrections_virt.cwiseAbs()).maxCoeff();
-
-  Index levelaboveqpmax = _rpamax - qpmax;
-  Index levelbelowqpmin = qpmin - _rpamin;
-
-  _energies.segment(0, levelbelowqpmin).array() -= max_correction_occ;
-  _energies.segment(qpmax + 1 - _rpamin, levelaboveqpmax).array() +=
-      max_correction_virt;
+  ShiftUncorrectedEnergies(dftenergies, qpmin, gwsize);
+}
+
+// Shifts energies of levels that are not QP corrected but
+// used in the RPA:
+// between rpamin and qpmin: by maximum abs of explicit QP corrections
+//                           from qpmin to HOMO
+// between qpmax and rpamax: by maximum abs of explicit QP corrections
+//                           from LUMO to qpmax
+void RPA::ShiftUncorrectedEnergies(const Eigen::VectorXd& dftenergies,
+                                   Index qpmin, Index gwsize) {
+
+  Index lumo = _homo + 1;
+  Index qpmax = qpmin + gwsize - 1;
+
+  // get max abs QP corrections for occupied/virtual levels
+  double max_correction_occ = getMaxCorrection(dftenergies, qpmin, _homo);
+  double max_correction_virt = getMaxCorrection(dftenergies, lumo, qpmax);
+
+  // shift energies
+  _energies.head(qpmin).array() -= max_correction_occ;
+  _energies.tail(_rpamax - qpmax).array() += max_correction_virt;
+}
+
+double RPA::getMaxCorrection(const Eigen::VectorXd& dftenergies, Index min,
+                             Index max) const {
+
+  Index range = max - min + 1;
+  Eigen::VectorXd corrections =
+      _energies.segment(min, range) - dftenergies.segment(min - _rpamin, range);
+
+  return (corrections.cwiseAbs()).maxCoeff();
 }
 
 template <bool imag>