Modifying SCF integrals

[Vsevolod]

Dear Dalton Community,

My name is Vsevolod, nice to meet you. I am interested in variation of electron mass and electron charge constants to observe any structural changes of some selected compounds. For that, I need to modify 1- and 2-electron integrals of SCF procedure and need some help on this way.

If not mistaken, I have already found 1-electron potential (POTINT) and kinetic energy (KININT) integrals in DALTON/abacus/her1int.F.
However, I am still struggling with 2-electron Vee term (Coloumb and Exchange) and Vnn term as average of nuclear repulsion.

Could you please help me find those integrals in the source code?
Or, if it is easier, to show how to modify respective 1- and 2-electron parts of the Fock matrices.

Thank you,
Seva

[hjaaj]

Well ... If m_factor is the electronic mass factor and e_factor is the factor on the electronic charge, I think the easiest is to modify the lines where the one-electron Hamiltonian is constructed by adding the kinetic energy integrals and the nuclear attraction integrals in .../DALTON/abacus/her1drv.F, that is, change

Code: Select all

              DO 800 I = 1, NNBAST
                 STHMAT(I,2) = STHMAT(I,2) + STHMAT(I,3)
 800          CONTINUE

to

Code: Select all

              DO 800 I = 1, NNBAST
                 STHMAT(I,2) = STHMAT(I,2)/m_factor + STHMAT(I,3)*e_factor
 800          CONTINUE

and in .../DALTON/sirius/sirgrad.F change in subroutine FCK2AO (which calculates the two-electron contribution to the Fock matrix):

Code: Select all

C
C *** End of subroutine FCK2AO
C
      CALL QEXIT('FCK2AO')
      RETURN
      END

to

Code: Select all

C
C *** End of subroutine FCK2AO
C
      e2_factor = e_factor**2
      call dscal(ndmat*n2basx,e2_factor, FCAO, 1)
      CALL QEXIT('FCK2AO')
      RETURN
      END

I think this will do what you want. If I understand you correctly, the Vnn term should not be changed becuase it does not depend on the electron mass nor on the electron charge.

[Vsevolod]

Dr. Jensen,

Thank you very much.