[Wien] optimization of a monoclinic structure

[Xavier Rocquefelte]

Dear Arnaud,

We have done such calculations few years ago in the case of LiMoS2 
material (space group : P-1). The main problem in such optimization of 
the unit cell is to optimized independently quantities that are 
dependent from each others.
One way to proceed is to optimize the cell parameters in an iterative 
way, as well  the cell parameter lengths as the angle values. Such 
calculations can take many times because for each minimum value of each 
parameter you need to check the other parameters.
Depending of your structure, such calculations can be very time 
consuming. In our case, the structure had a 2D character. Thus it was 
easier to find a global minimum.

In a general point of view, the more efficient way to proceed is to 
evaluate the stress tensor of the cell. Such feature is available in 
other codes such as abinit (that is free - gnu license). Today, I'm 
using such pseudopotential code for the geometry optimization and Wien2k 
for the chemical bond analysis and the properties simulations. The use 
of this two complementary tools is very powerful in terms of cpu time. 
Moreover, if you calculate the atomic force in the wien code using the 
pseudopotential optimized structure, the agreement is usually very good.

With my best regards

Xavier

Xavier Rocquefelte
Institut des Matériaux Jean Rouxel
Nantes, France



arnaud.vaseur at laposte.net a écrit:

> Dear WIEN2K users, I have question about optimization of an monoclinic 
> structure, so to do that have I to optimize c/a, v, b/a, v, ...., c/a, 
> v, b/a, v, in SCF manner until convergence of the structure or can I 
> perform just one  c/a, b/a, v optimization ? How can I to optimize 
> i.e. beta angel?  Any comments are welcome.
>
>  
>
> Thank you in advance    
>
>  
>
> Arnaud
>
>
>
> Accédez au courrier électronique de La Poste : www.laposte.net ;
> 3615 LAPOSTENET (0,34EUR/mn) ; tél : 08 92 68 13 50 (0,34EUR/mn) 


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