Re: [AMBER] ff14SBonlysc + OPC3

From: Matias Machado <>
Date: Mon, 29 Jun 2020 15:33:29 -0300 (UYT)

You are right Daniel, there is clearly no need for such parameter... however leap demands it in other cases (e.g. cyclopropane)... so there must be a magic hand behind such selectivity as the info isn't defined in frcmod files...

----- Mensaje original -----
De: "Daniel Roe" <>
Para: "AMBER Mailing List" <>
Enviados: Lunes, 29 de Junio 2020 14:54:57
Asunto: Re: [AMBER] ff14SBonlysc + OPC3

On Mon, Jun 29, 2020 at 1:03 PM Matias Machado <> wrote:
> An additional curiosity, neither "frcmod.opc3" nor "frcmod.tip3p" have angle definitions, I mean there is no angle at all, not even set to zero!

Note this is by design since TIP3P and OPC are rigid water models.
There is a "bond" between the hydrogens instead of an H-O-H angle.
This just makes it easier to apply the constraints to keep the water


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