[Pw_forum] Alterntive of Makov-Payne correction for noncubic systems

[Oliviero Andreussi]

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
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________________________________
From: pw_forum-bounces at pwscf.org <pw_forum-bounces at pwscf.org> on behalf of Amar Singh <amarsingh122014 at rediffmail.com>
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