[Pw_forum] help: the phonon calculation

[lan haiping]

On 8/28/06, hailin yu <yuhailin_79 at msn.com> wrote:
>
> Dear all:
>     I have some quesitons want to know. Can you tell me ? Thanks a lot!
> 1).Recently, I had calculated Ag3N which has the anti-ReO3 strucuture (i.e
> ,
> has the same structure with Cu3N,PRB 53,12648) by using CASTEP and found
> it's mechnical stabel  ( I find the elastic siffness coefficients of Ag3N
> satisfy the generalized elastic stability criteria). But when I calculated
> the phonon dispersion of Ag3N using PWSCF, I found there was a soft mode
> along G-X direcition (i.e the phonon frequency is negative). For a
> negative
> frequency appear, it means that the structure is not stable? If so, the
> results of CASTEP and PWSCF is confict? This quesiton is still confuzed me
> and I am eager to receive your reply. Thanks!



 you should give your input setting of calculation

2). For f-electronic materials (such as Pt), for their lattice dynamics
> properties, it is reasonable to calculate using PWSCF ?


as far as i know, there is no problem for pwscf to calculate metal's lattice
dynamics ,
since it is  Pseudopotential -plane wave method..


regards,

hai-ping

Thanks!
>
>     yuhailin
>
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