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Manual Pseudopotentials and orbitals Examples


4.7 Force calculation and structure relaxation


To calculate forces that the atoms experience, one needs to add a few more parameters in the INPUT file. Below is an example for the Si dimer.


suffix Si2_dimer
calculation relax
gamma_only 1
nstep 100
force_thr_ev 0.01
move_method cg
out_stru 1
trust_radius_ini 0.5


nstep the number of ionic iteration steps.
force_thr_ev the threshold for the force, below which the geometry relaxation is considered to be converged. The unit is eV/Angstrom.
move_method the algorithm used for geometry optimization. Possible choices are:
– cg : Conjugate Gradient (CG) algorithm
– bfgs : Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm
– sd : Steepest descend algorithm
          The CG method is recommended.
out_stru output the structure of each step or not.
trust_radius_ini the initial radius of the relaxation. We advise you not to change this parameter, unless you are sure that the initial structure is close to the final structure.




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