[Pw_forum] graphite cell optimization failed

[Chenghua Sun]

Deal All,

I didn't try QE4.3a yet, but I am wondering what is the theory basis for the first-principle vdW-DFT by 'vdW-DF' in QE 4.3a. Any improvement compared with semiempirical vdW scheme? In additional, is it applicable for all elements?

Cheers,
Chenghua

************************************************************
Chenghua Sun, PhD
Australian Institute for Bioengineering and Nanotechnology
Centre for Computational Molecular Science, Director
The University of Queensland
 
Postal Address: 
CCMS, AIBN Building #75, 
The University of Queensland
Brisbane, Qld 4072, Australia
 
Tel:   +61 7 3346 3972
Fax : +61 7 3346 3992
Email: c.sun1 at uq.edu.au 
Web: http://web.aibn.uq.edu.au/cbn
**************************************************************

________________________________________
From: pw_forum-bounces at pwscf.org [pw_forum-bounces at pwscf.org] On Behalf Of giuseppe.mattioli at mlib.ism.cnr.it [giuseppe.mattioli at mlib.ism.cnr.it]
Sent: Wednesday, 23 March 2011 7:12 PM
To: PWSCF Forum
Subject: Re: [Pw_forum] graphite cell optimization failed

Dear all
You can do better than the semiempirical "Grimme" correction. There is
a new ab initio van der Waals correlation functional implemented in QE
4.3a. Try    input_dft='vdW-DF', in the &sysytem list.
By the way, what about a (semiempirical or ab initio) vdW scheme in
cp.x? Is there any project going on?

Yours

Giuseppe

Quoting Masoud Nahali <masoudnahali at gmail.com>:

> Dear Eric
>
> Try london="true" to get improved answer; as you should know DFT is weak
> to calculate dispersion forces and by using the keyword one can include
> these forces semi-empirically. I hope it helps.
>
> Best Wishes
>
>  Masoud
> --------------
> Masoud Nahali, Sharif University of Technology
>
>
> Eric Wrote:
>
> Dear all,
>
> I'm trying to optimize unit cell parameter of graphite.
> The problem is the c axis gets too long.
> Starting from published data my initial parameters are a=4.59203 Bohr
> and c=12.513 Bohr.
> The final values are 4.664 and 15.829 respectively.
> I need someone to explain to me what I did wrong, I've attached my input
> file.
> That's a basic calculation so it's very frustrating to not make it done.
> I thank you in advance,
>
>                                      Eric.
>
> --
> /Be the change you wish to see in the world
> / --- Mahatma Gandhi ---
>
> Dr. Éric Germaneau <mailto:germaneau at gucas.ac.cn
> <http://www.democritos.it/mailman/listinfo/pw_forum>>
>
> College of Physical Sciences
> Graduate University of Chinese Academy of Sciences
> Yuquan Road 19A
> Beijing 100049
> China
>

Giuseppe Mattioli
ISM-CNR
Italy




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