Dear Amar,

Please remember to sign your next messages to the PW_forum with your full 
affiliation. I assume that your issues are with the convergence (not 
conversion) of the total energy with cell size. Makov-Payne correction is to 
correct the total energy of an isolated system (thus a system surrounded by 
vacuum), when modelled using periodic boundary conditions. It only works for a 
cubic cell, but since it is designed for an isolated system, it should not 
really matter which shape of unit cell you use.


Since you are requesting if you can use it with a different cell, I guess you 
want to converge the total energy of a periodic system, not of an isolated one, 
correct? Maybe a charged defect in a crystal? Whatever your problem is, if you 
want to simulate a non-isolated system, as far as I know, you have no clean way 
to correct for the pbc artefact, apart from increasing your cell size.


A not-so-clean approach could be to still use Makov-Payne correction for your 
bulk system, guessing an approximate dielectric constant for your crystal and 
applying the screened form of the correction. In this case you still do need to 
have a cubic unit cell though, and I would not guarantee on the meaningfulness 
of the results.


Best,


Oliviero Andreussi

--
Senior Postdoctoral Researcher
École Polytechnique Fédérale de Lausanne (EPFL) and
Università della Svizzera Italiana (USI) of Lugano
USI Campus, Via G. Buffi 17, 6904 Lugano, Switzerland
Emails: oliviero.andreussi @ epfl.ch -or- usi.ch
Tel: +41-(0)58-666-4810 / Skype: olivieroandreussi
Web: https://sites.google.com/site/olivieroandreussi

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________________________________
From: [email protected] <[email protected]> on behalf of Amar 
Singh <[email protected]>
Sent: Saturday, November 4, 2017 1:49:19 PM
To: pw_forum
Subject: [Pw_forum] Alterntive of Makov-Payne correction for noncubic systems

Dear Friends,
I want to optimize a structure with nonzero tot_charge and having issue with 
the conversion. I read on forum that Makov-Payne correction may help in 
conversion, but works only for cubic systems. Is there a way to use M-P 
correction for non-cubic system ? If not, what could be the next best possible 
alternative.
thanks
Amar


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