[gmx-users] 'constraints' directive and water

Justin Lemkul jalemkul at vt.edu
Tue Mar 27 21:11:54 CEST 2018

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

303 Engel Hall
340 West Campus Dr.
Blacksburg, VA 24061

jalemkul at vt.edu | (540) 231-3129


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