[CPMD-list] Re: CPMD-list

[Yong Kong]

Dear Mehmet and APSI,

Actually I met the same problem when I made test run on Si.
I guess you use a FCC cell containing 2 atoms. If you use 
a SC cell with 8 atoms, the results would be reasonable.
I think it may be the problem of single-k point (I am not sure).

By the way, the results on graphite is similar: The calculated  
bond length and interlayer spacing with hexagonal cell are much larger
than 1.421 and 3.35 Angstrom, but too smaller with an orthorhombic 
cell. 

So my question to APSI: what should I do? use multi-k points? It seems
that one can only do that with Lanczos diagonalisation. Is there other
methods to resolve this problem?

best regards

Yong




>Dear All,
>
>I am a bit puzzle to calculate lattice parameter of Si.
>Please see the below table. When I take bigger lattice
>parameter, the energy is getting smaller and smaller. 
>There should be turning point which is going to be 
>theoretical lattice parameter of Si. So any idea what could
>be the reason? or do i know something wrong?
>
> E_tot       a_lat
>-------      -----
>-7.14         5.0      
>-7.31         5.1
>-7.36         5.2
>-7.39         5.3
>-7.43         5.4
>-7.72         5.41    
>-7.73         5.42
>-7.74         5.43
>-7.74         5.44
>-7.75         5.45
>-7.78         5.5
>-7.83         5.6
>-7.87         5.7
>
>	-mehmet