Hi Francisco, You could indeed modify the constr.f file to include what you need, but first check the section of the manual entitled "Auxiliary Force Field". In there you can find a discussion of the MM.Potentials block, in which you can define the parameters of, among others, a harmonic potential.
Best regards, Alberto ----- El 11 de Noviembre de 2023, a las 09:13, Francisco Garcia <garcia.ff....@gmail.com> escribió: Dear Users, The constraint subroutine takes the form: subroutine constr( cell, na, isa, amass, xa, stress, fa, ntcon ). It doesn't contain information about energy. Now I am using a harmonic potential with a stiff spring to constrain a pair of atoms separated by a distance of r0. I should be able to pass the constraint harmonic energy V=1/2 * k * (rij - r0)^2 to the subroutine to be added to the total energy i.e., E + 1/2 * k * (rij - r0)^2 will be the total energy. Which routines should I modify to allow the total energy to account for the constraint energy? -- SIESTA is supported by the Spanish Research Agency (AEI) and by the European H2020 MaX Centre of Excellence (https://urldefense.com/v3/__http://www.max-centre.eu/__;!!D9dNQwwGXtA!V_yhBOHCFFxdY5WMcg2Vv8Ymb5CUuYr4dpyQyrnB8zQRuVGasPatUDFCuulHsnFCbVfyyrstpp82eApPAg3lvMc$ )
-- SIESTA is supported by the Spanish Research Agency (AEI) and by the European H2020 MaX Centre of Excellence (http://www.max-centre.eu/)
