mirror of https://github.com/abinit/abinit.git
49 lines
1.8 KiB
Markdown
49 lines
1.8 KiB
Markdown
---
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description: How to select the SCF algorithm
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authors: XG
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---
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<!--- This is the source file for this topics. Can be edited. -->
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This page gives hints on how to select the SCF algorithm with the ABINIT package.
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## Introduction
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Self-Consistent Field calculations allow to determine the solution of the
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Kohn-Sham equations, ending with converged "self-consistent" wavefunctions,
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density, and Kohn-Sham potentials.
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Different algorithms can be chosen to
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converge to the solution of this set of equations.
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The input variables [[iscf]] governs
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the choice of density/potential
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self-consistency algorithms, while [[wfoptalg]] focuses on the determination
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of the wavefunction through the solution of the Schrodinger equation with fixed
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Kohn-Sham potential.
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In the first class of algorithms, selected by [[iscf]]), Pulay
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mixing is one of the most efficient. Also, an efficient preconditioner will
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speed up the convergence. Among different choices, a generalized Kerker
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preconditioner is implemented, see [[diemac]], [[diemix]] and [[dielng]].
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In order to perform a non-self-consistent calculations of wavefunctions and
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corresponding eigenvalues in a fixed potential, as for representing a full
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band structure, the loop over density/potentials self-consistency must be
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disabled, for which [[iscf]]=-2 must be chosen.
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Among the algorithms to find the wavefunctions, selected by [[wfoptalg]], the
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conjugate-gradient and the LOBPCG ones are the favourite.
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The RMM-DIIS algorithm is faster, but might be unstable. Use it for molecular dynamics run
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or long geometry optimizations. Use the Chebyshev filtering for massive parallel runs.
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Inner electronic eigenvalues can be computed thanks to the minimisation of the
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residual with respect to a target energy value, see [[eshift]].
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## Related Input Variables
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{{ related_variables }}
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## Selected Input Files
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{{ selected_input_files }}
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