Re: [AMBER] Monte Carlo Steps in Constant pH simulation

From: Adrian Roitberg <>
Date: Wed, 12 Jan 2011 11:52:23 +0100

Page 139 in the manual, usually a good source of information.

"You must also specify the period for Monte Carlo steps, ntcnstph (for
period n, a Monte Carlo step is performed every n steps). Note that only
one residue is examined on each step, so you should decrease the step
period as the number of titrating residues increases to maintain a con-
stant effective step period for each residue. We have seen good results
with fairly short periods, in the neighborhood of 100 fs effective
period for each residue (e.g. ntcnstph=5, dt=0.002 with about 10
residues titrating)."

On 1/12/11 11:27 AM, nicholus bhattacharjee wrote:
> Dear community,
> I want to know in constant pH simulations which
> option in the input controls the number of Monte Carlo Steps? For example my
> input file is
> Test of constant pH in GB on HEWL
> &cntrl
> ig=49,
> nstlim =2500000
> cut=30.0, scee=1.2, igb=2, saltcon=0.1,
> ntx=1, irest=0, ntb=0, ntpr=500,
> dt=0.002, nrespa=1,
> ntt=1, tempi=300.0, temp0 = 300., tautp=2.0,
> ntc=2, ntf=2, tol=0.000001,
> ntwr =500, ntwx=500, rgbmax=30.0
> icnstph=1, ntcnstph=1, solvph=1.0
> /
> In the cpout file I am getting 499 delta records after each full record i.e.
> after every 500 steps
> Thank you for your answer in advance.

                            Dr. Adrian E. Roitberg
                              Associate Professor
                Quantum Theory Project, Department of Chemistry
                            University of Florida
   Senior Editor. Journal of Physical Chemistry.
on Sabbatical in Barcelona until August 2011.
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Received on Wed Jan 12 2011 - 03:00:03 PST
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