WIEN2k-FAQ: Minimization of forces
©2001 by P. Blaha, K. Schwarz and J. Luitz
In order to optimize internal positions you need "free" structural
parameters. ( A spacegroup with a position "x"). In high symmetry cases you may need to break
symmetry (move an atom away from its ideal position like 0.25,0,0) before you initialize WIEN. (You need a L=1 component in case.in2)
- There are 2 methods implemented in WIEN2k:
- Always run a structure to scf, call a program which uses the resulting
forces, generates a new struct file and run another scf cycle. This procedure
is implemented as an option in W2web (Execution/mini. positions) or
you can use min_lapw at the command line.
- The alternative (and usually much more efficient) method is to fuse the
scf and position optimization loop into one long loop (sometimes hundreds of
iterations). It can also be chosen from w2web or on the command line you can
use run(sp) -min. Often it is better to do first a couple of scf
cycles without -min (eg. 10), and only later on start the fused minimization
eg. with touch .minstart.
- In case of troubles, please consult the UG (minimization), where a detailed
description of possible problems and their solution is given.