Narrow escape problem in two-shell spherical domains

Codes used in the scientific publications:
[1] M. Mangeat and H. Rieger, The narrow escape problem in a circular domain with radial piecewise constant diffusivity, J. Phys. A: Math. Theor. 52, 424002 (2019). Preprint available on arXiv.
[2] M. Mangeat and H. Rieger, Narrow escape problem in two-shell spherical domains, Phys. Rev. E 104, 044124 (2021). Preprint available on arXiv.
Written by M. Mangeat (2021).

Finite Element Method (FEM)

Contains the FreeFem++ codes. Calculate the numerical solution of the MFPT with the finite element method.
Run: FreeFem++ -v 0 -nw NEP2d_twoshell_FEM.edp -parameter value.
List of parameters: epsilon, Delta, D1, D2, V1, V2, Nvert, err, expT, expNE, expDELTA, expMAX (details as comments in the code).

Kinetic Monte-Carlo (KMC)

Contains the C++ codes. Calculate the MFPT via the stochastic simulations of Brownian particles.
Compile: g++ NEP2d_twoshell_KMC.cpp -lgsl -lgslcblas -lm -O3 -s -o NEP2d_twoshell_KMC.out.
Run: ./NEP2d_twoshell_KMC.out -parameter=value.
List of parameters: epsilon, Delta, D1, D2, V1, V2, Npart, ran (details as comments in the code).