From: JC Gumbart (gumbart_at_ks.uiuc.edu)
Date: Wed Jul 30 2014 - 10:27:16 CDT
> Though if you're using the CHARMM force field, it's actually recommended to instead use
> rigidBonds all
> because that's what the force field is parametrized for.
I thought this was only the case when using a 2-fs time step?
On Jul 30, 2014, at 12:21 AM, Kenno Vanommeslaeghe <kvanomme_at_rx.umaryland.edu> wrote:
> On 07/29/2014 06:59 PM, Hadi wrote:
>> Below you can find the parameters of the modified TIP3P model (CGenFF:
>> Parameters for the Charmm General Force Field). This model is often used
>> in NAMD.
>
> (1) Small detail: the only thing this has to do with CGenFF is that it is the water model on which *all* the all-atom additive CHARMM force fields are based, the first one of which predates CGenFF by roughly 15 years. The confusion likely arises from the fact that the NAMD version of the CHARMM water stream file can currently be found on my CGenFF page. Instead, we probably should put it on the main CHARMM force field page alongside the CHARMM version.
>
> (2) It is my understanding that the parameters you copy-pasted into your e-mail are just "reasonable values" for in case an MD engine or methodology is used that does not support rigid water. They won't give the exact same properties as the true rigid TIP3P model. NAMD, however, does support rigid water; assuming the psf is generated correctly, all one need to do is put the following line in the NAMD input:
> rigidBonds water
> Though if you're using the CHARMM force field, it's actually recommended to instead use
> rigidBonds all
> because that's what the force field is parametrized for.
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