Re: [AMBER] ff19SB + BSC1 + OPC + which ions ?

From: David A Case <>
Date: Sun, 29 Mar 2020 10:36:29 -0400

On Sun, Mar 29, 2020, Vlad Cojocaru wrote:
>Second question comes from the fact that while loading the OPC water
>model, I noticed that  leaprc.water.opc file does not load the Li&Merz
>ions for the OPC model (frcmod.ions1lm_126_hfe_opc). Instead, it is
>loading the Joung-Chetham monovalent ions for TIP4PEW

The default choice for all water molecules (except tip4pd) is to use the
Joung-Cheatham parameters for monovalent ions, using Li&Merz parameters
for higher charges. As I remember, this was primarily because we had
much more experience with the behavior of the JC parameters -- which
becomes a bit of a self-fulfilling goal, since most people will use
default parameters.

My reading of the experience that we do have is that Li&Merz are not
much different from JC for monovalents, but others with more direct
experience may wish to chime in here.

Of course, you are welcome to override the defaults if you wish.


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Received on Sun Mar 29 2020 - 08:00:02 PDT
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