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Re: a bug or a feature?

From: Markus Deserno
Subject: Re: a bug or a feature?
Date: Fri, 16 Apr 2021 09:51:26 -0400


I cannot conceive of a single instance where I wanted to know a
bond distance but would NOT want the minimum image convention
applied. Note that I specifically said “BOND DISTANCE”. there are
many situations where I care about a DISTANCE and I do NOT
want the minimum image convention. But for bonds it never seems
to make sense to not first apply it.

So I’d be inclined to call it a "feature”.


Dr. Markus Deserno ++1-412-268-4401 (office)
Professor of Physics ++1-412-681-0648 (fax)
Carnegie Mellon University ++1-412-268-8367 (Theresa Gabrielli)
5000 Forbes Avenue
Pittsburgh, PA 15213, USA

On Apr 16, 2021, at 6:46 AM, Peter Košovan <> wrote:

Dear Espresso developers,

Today, we noticed an unexpected behaviour of Espresso, that I would consider a bug, but it might also be a feature. Before submitting a bug report, I want to ask your opinion.

In brief: if two particles connected by a bond but they are found in different periodic copies of the simulation box, then Espresso runs without any error or warning. Since particles are internally represented in unfolded coordinates, I would expect to get a "bond broken" error if the (unfolded) distance is greater than box_l/2. Apparently, minimum image convention is used also in the calculation of bond distances, which makes no sense in the unfolded coordinates.

If we agree that such behaviour is undesired, I will submit a bug report and a minimal working example.

With regards,


Dr. Peter Košovan

Department of Physical and Macromolecular Chemistry
Faculty of Science, Charles University in Prague, Czech Republic

Katedra fyzikální a makromolekulární chemie
Přírodovědecká fakulta Univerzity Karlovy v Praze
Tel. +420221951029
Fax +420224919752

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