This page gives hints on how to perform a geometry optimization with the ABINIT package.
Different algorithms (Broyden; modified Broyden; Verlet with sudden stop of atoms, FIRE) allows to find the equilibrium configuration of the nuclei, for which the forces vanish, see ionmov. The cell parameters can also be optimized concurently with the atomic positions optcell, possibly with a state of given stress as a target, strtarget.
Specified lattice parameters, or angles, or atomic positions, can be kept fixed if needed, see topic_GeoConstraints.
A genetic algorithm has been coded, for global optimisation. See ga_rules. Not in production yet.
The results of the structural relaxation are saved in the HIST.nc file. This file can be used to restart the calculation or to analyze the results at the end of calculation. For further details about the AbiPy API please consult the HistFile notebook .
When performing cell parameter optimization, the default setting of ABINIT will not permit increase of the lattice parameters from the initial ones. One needs to set dilatmx to some value larger than the default 1.0 . If the starting lattice parameters are thought to be accurate and should not increase by more than 5%, set dilatmx to 1.05 , which will lead to a moderate increase of CPU time by about 15% . If the starting lattice parameters are just a guess, perform a first run with chkdilatmx=0 . This will yield an estimate of the correct lattice parameters, but such estimate are not the numerically exact ones for the ecut value. You are done if you do not need accurate geometry estimation anyhow. Otherwise, after this first run, perform a second run by restarting from the newly estimated value, with chkdilatmx=1 and dilatmx to 1.05 .
Related Input Variables¶
- dilatmx lattice DILATation: MaXimal value
- ntime Number of TIME steps
- strfact STRess FACTor
- tolmxde TOLerance on the MaXimal Difference in Energy
- tolmxf TOLerance on the MaXimal Force
- iprcfc Integer for PReConditioner of Force Constants
- restartxf RESTART from (X,F) history
- strprecon STRess PRECONditioner
- strtarget STRess TARGET
- chkdilatmx CHecK DILATMX
- expert_user EXPERTise of the USER
- fxcartfactor Forces to (X) CARTesian coordinates FACTOR
- ga_algor Genetic Algorithm - ALGOrithm selection
- ga_fitness Genetic Algorithm FITNESS function selection
- ga_n_rules Genetic Algorithm Number of RULES
- ga_opt_percent Genetic Algorithm OPTimal PERCENT
- ga_rules Genetic Algorithm RULES
- goprecon Geometry Optimization PRECONditioner equations
- goprecprm Geometry Optimization PREconditioner PaRaMeters equations
- random_atpos RANDOM ATomic POSitions
Selected Input Files¶