[Wien] Cohesive energies in WIEN2k

[Andrzej Koleżyński]

>>> (4) Finally, why should the single atom at the origin be placed inan FCC  lattice and not a Simple Cubic lattice say ? In other words why FCC and not
>>>some 
>>>  other lattice.
>>>      
>>>
>>I admit I do not get that point either, although I suspect it to be
>>simple. I would think that for a given lattice constant the interatomic
>>separation is largest in simple cubic?
>>    
>>
>
>The point is: fcc is a "close packed lattice", thus for a given 
>"nn-distance" (not lattice parameter, which you will adjust to get the 
>desired nn-distance) you will get the smallest "volume" 
>of the unit cell and thus the most economical calculation.
>
>
>  
>
Some time ago, I made some tests for SC, BCC and FCC structures, for 
identical "nn-distance". The calculated energies were practically 
identical - only cpu times were different.
So basically you can use any structure you want, but most effective is 
FCC one.

Andrzej Kolezynski
Faculty of Materials Science and Ceramics
University of Science and Technology AGH-UST
Al. A.Mickiewicza 30, 30059 Krakow, POLAND