This page gives hints on how to select the SCF algorithm with the ABINIT package.
Self-Consistent Field calculations allow to determine the solution of the Kohn-Sham equations, ending with converged “self-consistent” wavefunctions, density, and Kohn-Sham potentials. Different algorithms can be chosen to converge to the solution of this set of equations, governed by the input variable iscf and wfoptalg. iscf focuses on the density/potential self-consistency algorithms, while wfoptalg focuses on the determination of the wavefunction through the solution of the Shrodinger equation with fixed Kohn-Sham potential.
The algorithm selected by iscf are the iterative kind, among which Pulay
mixing is one of the most efficient. Also, an efficient preconditioner will
speed up the convergence. Among different choices, a generalized Kerker
preconditioner is implemented, see diemac, diemix and dielng.
In order to perform a non-self-consistent calculations of wavefunctions and corresponding eigenvalues in a fixed potential, as for representing a full band structure, the loop over density/potentials self-consistency must be disabled, for which iscf=-2 must be chosen.
Among the algorithms to find the wavefunctions, selected by wfoptalg, the conjugate-gradient and the LOBPCG ones are the favourite. Use the Chebyshev filtering for massive parallel runs.
Inner electronic eigenvalues can be computed thanks to the minimisation of the residual with respect to a target energy value, see eshift.
Related Input Variables¶
- dielng model DIElectric screening LeNGth
- diemac model DIElectric MACroscopic constant
- diemix model DIElectric MIXing factor
- npulayit Number of PULAY ITerations for SC mixing
- densfor_pred DENSity and FORces PREDictor
- diecut DIElectric matrix energy CUToff
- diegap DIElectric matrix GAP
- dielam DIElectric matrix LAMbda
- eshift Energy SHIFT
- iprcel Integer for PReConditioning of ELectron response
- isecur Integer for level of SECURity choice
Selected Input Files¶