Re: [AMBER] NonUniversalWarning: Modified off-diagonal LJ parameters detected

From: David A Case <>
Date: Sat, 16 Jan 2021 14:22:39 -0500

On Sat, Jan 16, 2021, Loki wrote:
>>NonUniversalWarning: Modified off-diagonal LJ parameters detected
>You may ignore this message: it's expected with CHARMM force fields.
>Could I please ask why?

There may be two types of questions here:

1. What is a "modified off-diagonal" LJ term?

     Generally, force fields assign epsilon and Rmin parameters to atom types.
     The LJ parameters for interactions between two different atoms types
     are determined by so-called mixing rules. A "modfied" LJ parameter sets
     specific epsilon/Rmin parameters for interactions between a pair of
     atom types, over-riding the use the the usual mixing rules.

2. Why did the CHARMM developers decide to incorporate these into their FF?

     I don't know. You'd have to read the papers that describe the
     particular CHARMM FF you are using.

....hope this helps...dac

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Received on Sat Jan 16 2021 - 11:30:02 PST
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