[gmx-users] 'constraints' directive and water
nedomacho at gmail.com
Tue Mar 27 21:24:54 CEST 2018
My idea about SETTLE probably comes from misunderstanding of the fact
that I do not have FLEXIBLE defined anywhere and the following excerpt
[ settles ]
; OW funct doh dhh
1 1 0.09572 0.15139
[ bonds ]
; i j funct length force.c.
1 2 1 0.09572 502416.0 0.09572 502416.0
1 3 1 0.09572 502416.0 0.09572 502416.0
On 3/27/2018 1:18 PM, Alex wrote:
> That was always my default impression, but from looking into e.g.
> tip4p.itp i somehow got the idea that water _is_ affected by
> Yes, whenever I have hydrogens in the system (aside from water), I
> always set 'h-bonds', which, if you recall my old 'meh' regarding
> constraints, suggests that I have accepted your view for computational
> efficiency. :) This certainly answers my question, thank you.
> On 3/27/2018 1:11 PM, Justin Lemkul wrote:
>> On 3/27/18 3:10 PM, Alex wrote:
>>> Hi all,
>>> Some of my simulations run with a time step of 2 fs and
>>> 'constraints' set to 'none'. Everything runs perfectly fine, but
>>> with such a time step, do you usually set constraints to 'h-bonds'?
>>> I know I should be looking at literature for this, but just wanted
>>> to get a basic idea on whether people do this.
>> Normally constraining bonds to H is required to get stable
>> integration with dt = 2 fs. Water is a different matter; it is held
>> rigid with SETTLE and is not under the influence of the "constraints"
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