SCF with zero iterations

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Sep 21, 2021, 9:37:02 PMSep 21
to dirac-users
Dear Dirac Experts,

is it possible in Dirac just to load orbitals (from DFCOEF, DFPCMO or DFACMO), re-compute SCF energy, but do no SCF iterations and let these orbitals to be accepted in further post-HF calculations as converged?

Maybe, I will set ?
1D+10 1D+10

I am interested in this in particular as I have some D17 computed orbitals and would like to compare SCF energy with D19 version, but keep the orbitals the same (no iterations, but SCF energy to be recomputed, not just read-in from DF* file).

Best regards,

Trond SAUE

Sep 22, 2021, 6:20:05 AMSep 22

HI Jakub,

in each SCF iteration, DIRAC will build the Fock-matrix and then calculate the energy. It then checks for convergence. If convergence, the cycle will exit. If not, DIRAC proceeds to diagonalization of the Fock matrix in orthonormal basis.

This means that if you read in a set of coefficients, DIRAC will calculate the energy associated with these coefficients. You can check orbital energies and the coefficients themselves through the analysis module.

If DIRAC finds that the calculation has converged, it will stop and print the usual information about total and orbital energies and you have your original coefficients.

If DIRAC finds that the calculation has not converged, it will proceed to diagonalization, so you get new coefficients.

For your purpose you can either play with the convergence thresholds, as you suggest, or you can play with the MAXITR keyword.

All the best,


Trond Saue
Laboratoire de Chimie et Physique Quantiques
UMR 5626 CNRS --- Université Toulouse III-Paul Sabatier
118 route de Narbonne, F-31062 Toulouse, France

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