Re: [AMBER] ff12SB with Na+ ion

From: Marc van der Kamp <>
Date: Wed, 25 Apr 2012 12:10:38 +0100


This question has been answered numerous times on the list, most recently
less than 24hrs ago...

The key is to load the ion parameters relevant for the water model you use.

Below is the answer to a similar question from yesterday, posted by InSuk
Joung :


The correct way to load the force modification file is typing

loadamberparams frcmod.ionsjc_spce

as a command of leap.
Be careful that there are two other parameter files: frcmod.ionsjc_tip3p
and frcmod.ionsjc_tip4pew.
You need to choose one depending on the water model you use. The parameters
were optimized for SPC/E, TIP3P, and TIP4Pew water models, respectively.
See the reference for more details:

On 25 April 2012 11:56, Tong Zhu <> wrote:

> Dear everyone,
> when I use amber ff12SB force field I want add two Na+ ions to my
> system, but tleap can't save top and crd files, and gives the following
> massage:
> For atom: .R<Na+ 762>.A<Na+ 1> Could not find type: Na+
> How can I fix this problem??
> Thank you very much ~~~
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Received on Wed Apr 25 2012 - 04:30:03 PDT
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