[Pw_forum] Conversion of del(E)/V to P(stress)

Nicola Marzari nicola.marzari at epfl.ch
Tue Aug 8 16:48:32 CEST 2017

On 08/08/2017 16:25, Afshin Arjangmehr wrote:
> Dear QE users and developers,

First thing, trying raising you cutoffs (e.g. use pseudo and
suggestions from materialscloud.org/sssp, and/or even higher).

The stress tensors converges slowly with the cutoff.


> I have a question regarding calculation of elastic constants in metallic 
> alloys. When I use tstress=.TRUE. to calculate stress alongside total 
> energy, in -2%<strain<+2% range (elastic region), I expect to have a 
> linear variation of stress with strain but my results indicate a totally 
> non-linear correlation.
> I use the E/V vs. strain curve to calculate elastic constants and my 
> results are consistent with experimental reports. Only, the stress part 
> calculated within pw.x simulation seems to be incorrect. Now:
> 1- Am I missing anything besides "tsress" in my input file?
> 2- Would it be correct if I manually convert E/V (delta(Energy)/Volume) 
> to P(stress)? and if yes, how?
> Thank you very much.
> Afshin
> -- 
> With Best Regards
> Afshin Arjhangemehr
> PhD candidate in Radiation Application
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Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, EPFL
http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project

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