[gmx-users] 'constraints' directive and water

[Justin Lemkul]

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" keyword.

-Justin

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Justin A. Lemkul, Ph.D.
Assistant Professor
Virginia Tech Department of Biochemistry

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