[Pw_forum] How to calculate Mean Square Displacement (MSD)

[Nam Tran]

Dear Lorenzo and Pascal


Thank you so much for your kind replies.


Best Regards,

Nam Tran

________________________________
From: pw_forum-bounces at pwscf.org <pw_forum-bounces at pwscf.org> on behalf of Lorenzo Paulatto <paulatz at gmail.com>
Sent: Monday, October 30, 2017 7:10:17 PM
To: pw_forum at pwscf.org
Subject: Re: [Pw_forum] How to calculate Mean Square Displacement (MSD)

On 30/10/17 08:29, Nam Tran wrote:
> I do not know whether I should consider the distance with atom that goes
> about outside the box (a) or its image (b). Please check the image below

Usually the right thing is to consider the smallest of all the possible
distances. I.e. you put the red atom in all the positions which are
equivalent by periodic boundary conditions, these in principle are
infinite but going up to the second neighboring cell is usually more
than enough; for each case you take the distance with the blue atom, and
you take the minimum of all the distances.

kind regards


--
Lorenzo Paulatto - Paris
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