WIEN2k-FAQ: Minimization of forces

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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:
- The new (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 iterations or use -fc 10), and only later on start the fused minimization eg. with touch .minstart while the scf cycle is still running.
- The old (conventional) method always runs a structure to scf, calls a program which uses the resulting forces, generates a new struct file and runs another scf cycle. This procedure is implemented as an option in W2web (Execution/mini. positions) or you can use the script min_lapw at the command line.
In case of troubles, please consult the UG (minimization), where a detailed description of possible problems and their solution is given.

Peter Blaha,