[Pw_forum] how to treat free electron gas, especially how to setup input file

[Lorenzo Paulatto]

On Tue, 03 Jan 2012 18:42:52 +0100, Jun Liu <jun.physics at gmail.com> wrote:
> Let me wish all of you a Happy New Year first.

Thnak you, a happy new too you as well.

> The code itself
> should be well-defined for a lattice system, so how is the code adapted  
> to the free electron problem?

In principle, if you set ntyp=0, nat=0 and nelec>0 and  
input_dft='whatever' the code will perform a calculation for a free  
electron gas in the unit cell you specify with the functional you  
selected. It will of course assume a positive-charged background to keep  
the total charge neutral. For a large enough unit cell, this should tend  
to an actual free-electron gas.

However, keep in mind that this feature is very rarely used, so you could  
incur in some unknown bug. Take care to test it for consistency on  
simple/well known cases before.

best regards


-- 
Lorenzo Paulatto IdR @ IMPMC/CNRS & Université Paris 6
phone: +33 (0)1 44275 084 / skype: paulatz
www:   http://www-int.impmc.upmc.fr/~paulatto/
mail:  23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05