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

From: Vlad Cojocaru <>
Date: Sun, 29 Mar 2020 17:27:36 +0200

Thanks David,

If course I know I can use whatever set of parameters ... I was just wondering whether there is a reason specifically related to the OPC water model .... Because the ion parameters are water model specific but the OPC water model is loaded with J&C ions for a different water model whereas L&M ions are available for OPC ...


On 29 March 2020 16:36:29 CEST, David A Case <> wrote:
>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
>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.
>AMBER mailing list

Sent from my Android device with K-9 Mail. Please excuse my brevity.
AMBER mailing list
Received on Sun Mar 29 2020 - 08:30:02 PDT
Custom Search