[Wien] structure optimization in WIEN2k

[Hong Jiang]

Dear WIEN2k users,
I have a question about the structure optimization using WIEN2k. I want 
to optimize a crystal structure, say, tetragonal ZrO2,
which has three structural variables, the two lattice constants a, c,  
and an internal variable d_z.  WIEN2k provides the functions of
 (1) optimize volume with fixed c/a ratio
 (2) Optimize c/a ratio with fixed volume
 (3) optimize internal variables with fixed lattice constant,
I guess taking different order of these optimization procedures would 
lead to different results. Ideally I guess one should repeat these three 
procedures
for several times until convergence is reached.
My questions are : are  there any empirical schemes to obtain the 
optimized structure more efficiently ? Is the self-consistency really 
necessary?
If not,  which order should one take to obtain the most reliable results?

Thank you very much in advance!

  -Hong Jiang