The ABINIT Users Mailing List ( CLOSED )

[Masayoshi Mikami <mmikami@rc.m-kagaku.co.jp>]

Dear Xiang,

I am not in the position to reply to your questions always,
in principle. (Here is just a forum ML, not a support desk...)

But my suggestions are:

- Please be aware of the message (in red !) on the ABINIT website
(Pseudopotentials web pages), namely,
"Use at own risk !
Pseudopotentials should always be tested in well-known situations,
before using them for predictions"
If they did not work for you, you might want to make your own
pseudopotentials. As I said, please visit FHI98PP  and/or OPIUM site.

- When you could have your own PP, you could try benchmarks
with well-known situation, e.g. Y2O3, Ta2O5 (binary compounds).
Then if the benchmarks would seem OK, you could move forward
to the ternary case (YTaO5). After having such "step-by-step"
process, you could come back again.

- Please, do not have multiple posts ... netiquette !
(I do not like to see four similar messages at one time ... :-( )

Good luck,
Masayoshi

P.S. Please read again my posts ... nothing left unsaid:
http://www.abinit.org/wws/arc/forum/2007-06/msg00020.html
http://www.abinit.org/wws/arc/forum/2007-06/msg00082.html

On 2007/06/20, at 12:16, xd0533@163.com wrote:

> dear users;
>    When I do YTaO4 geometry optimization,my result of acell is  
> always in worse
> agreement with experimental value.It is about 10% error.This error  
> is very
> large.In order to reduce the error,I try different kinds of  
> method.Such as
> changing xc,pseudopotentials(FHI(GGA),TM,HGH(LDA,semi-core)) and so  
> on.But
> there is no effect.The input file I have attached in
> http://www.abinit.org/wws/arc/forum/2007-06/msg00075.html I try to  
> increase
> convergence criterion.But I think this is not sticking point.
> The structure of YTaO4 is monoclinic.Now I have an idea.I don't  
> know whether
> it is reasonable.My idea is:first,I use optcell=0 to modify nuclear
> positions,second I use optcell=1 to optimize volume and acell,but  
> optcell=1
> doesn't optimize rprim,so next step I use optcell=3 to optimize  
> rprim.Because
> for second step,I have optimized volume,so in the third step I can fix
> volume.I don't know whether my idea is reasonable.I hope to get  
> your help.
> Thank everyone for answering my question.
> Best Wish!
> xiang
> To:Masayoshi Mikami
> I have seen your article of calculation Y2O2S.Your result of acell  
> is in good agreement with experimental value.This shows TM  
> pseudopotential of Y is reasonable.And I saw article about KTaO3.He  
> also uses TM pseudopotentials.So I believe TM pseudopotentials of  
> YTaO4 is reasonable.But why is my result so bad?
> What is your opinion about this problem,Mr Masayoshi Mikami.I hope  
> your reply!
> Thanks a lot!