mirror of https://github.com/abinit/abinit.git
37 lines
1.3 KiB
Markdown
37 lines
1.3 KiB
Markdown
---
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description: How to constrain the geometry of the system in geometry optimization, molecular dynamics or searches
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authors: GG
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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 constaint the geometry of the system in geometry optimization, molecular
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dynamics or searches with the ABINIT package.
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## Introduction
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There are two mechanisms to put constraints on the atom positions in ABINIT.
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They can be used in [[topic:GeoOpt|geometry optimization]],
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[[topic:MolecularDynamics|molecular dynamics]] (including PIMD) or other
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geometry algorithms (e.g. [[topic:TransPath|transition path searches]]).
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The simplest one (entry point [[iatfix]]) simply define a set of atoms that
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are fixed, either entirely, or only along one of the directions (for the
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latter, see the warning in [[iatfix]])
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A more complex one, but also much more powerful, allows to place constraints
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on linear combinations of atomic positions. Thanks to such constraint, the
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mean position of two atoms (or a fragment, like a molecule) can be fixed, or
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constrained to stay within an arbitrary plane. One can thus also sample
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different mean positions. See a complete description in [[wtatcon]].
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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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