SCFAlgorithms

This page gives hints on how to select the SCF algorithm with the ABINIT package.

Introduction

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. The input variables iscf governs the choice of density/potential self-consistency algorithms, while wfoptalg focuses on the determination of the wavefunction through the solution of the Schrodinger equation with fixed Kohn-Sham potential.

In the first class of algorithms, selected by iscf), 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. The RMM-DIIS algorithm is faster, but might be unstable. Use it for molecular dynamics run or long geometry optimizations. 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

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