Re: FEP calculations: optimizing the dlambda, number of steps

From: Shyno Mathew (sm3334_at_columbia.edu)
Date: Thu Nov 21 2013 - 13:33:34 CST

Hey Jerome,
thanks again fro your reply.
When I plot the probability distribution for different consecutive lambda
windows, most plots show good overlap except the following:
lambda from 0.45 to 0.5 and lambda from 0.5 to 0.55.
So I am looking into the option of reducing dlambda for the window 0.45 to
0.55. It seems in gibbs (AMBER module for FEP) there is an option of doing
FEP with dynamically modified windows.
Is there anything like this in namd?

thanks,
Shyno

On Tue, Nov 19, 2013 at 5:25 AM, Jrme Hnin <jerome.henin_at_ibpc.fr> wrote:

>
> > The column before temperature is the average change in potential energy
> > (deltaUavg) and the column preceding it is the change in potential energy
> > (delta U). Is this correct?
>
> Yes, that is correct.
>
> Jerome
>
>
> > On Mon, Nov 18, 2013 at 6:32 PM, Jrme Hnin <jerome.henin_at_ibpc.fr>
> wrote:
> >
> > > Hi,
> > >
> > > AlchDecouple only makes a difference if there are nonbonded
> interactions
> > > within the perturbed groups.
> > >
> > > "AlchDecouple on" means that these interactions are unperturbed, so
> that
> > > the "intact" molecule is decoupled from its environment.
> > > "AlchDecouple off" means that the molecule's nonbonded interactions
> > > (included its self-interactions) are perturbed.
> > >
> > > Jerome
> > >
> > >
> > > ----- Original Message -----
> > > > also, can some one explain the parameter "AlchDecouple"
> > > > I have done runs with both " alchDecouple on" and "alchDecouple
> off", but
> > > > didn't notice any difference while plotting delta G vs. deltalambda
> > > values.
> > > >
> > > > Any help will be really appreciated,
> > > >
> > > > thanks,
> > > > Shyno
> > > >
> > > >
> > > > On Mon, Nov 18, 2013 at 12:44 PM, Shyno Mathew <sm3334_at_columbia.edu>
> > > wrote:
> > > >
> > > > > Hello all,
> > > > > I think I figured out the answers
> > > > > The column before temperature is the average change in potential
> energy
> > > > > (deltaUavg) and the column preceding it is the change in potential
> > > energy
> > > > > (delta U). So I should calculate the variance of delta U values to
> > > optimize
> > > > > delta lambda, length of each window?
> > > > > Could some one confirm this?
> > > > >
> > > > > thanks,
> > > > > Shyno
> > > > >
> > > > >
> > > > > On Fri, Nov 15, 2013 at 4:02 PM, Shyno Mathew <sm3334_at_columbia.edu
> >
> > > wrote:
> > > > >
> > > > >> Dear all,
> > > > >> I am doing the FEP calculations and need some help in
> understanding
> > > the
> > > > >> .fepout file.
> > > > >> 1. this is the first part of .fepout file
> > > > >> # STEP Elec vdW dE dE_avg Temp dG
> > > > >>
> > > > >> # l l+dl l l+dl E(l+dl)-E(l)
> > > > >>
> > > > >>
> > > > >> #NEW FEP WINDOW: LAMBDA SET TO 0 LAMBDA2 0.05
> > > > >> FepEnergy: 0 -469793 -469790 34401.03 34399.75 0.8153 0.8153
> 298.6998
> > > > >> 0.8153 FepEnergy: 100 -472878 -472876 33902.44 33900.11 0.4059
> 0.3622
> > > > >> 313.4741 0.1558 FepEnergy: 200 -472922 -472919 33338.32 33336.3
> > > 0.8862
> > > > >> 0.1122 312.7195 -0.3716
> > > > >> I understand the penultimate column is temperature and the last
> > > column is
> > > > >> dG value. What exactly are the other columns?
> > > > >>
> > > > >> 2. I am trying to see what dlambda, number of steps will give me
> > > accurate
> > > > >> results.
> > > > >> Following article says keeping the variance at each stage on the
> > > order of
> > > > >> 1-2 KT usually guarantees good overlap between probability
> > > distributions
> > > > >> in
> > > > >> two consecutive strata and a reliable error estimate.
> > > > >> Here the variance means the variance of dG values (only of the
> > > ensemble
> > > > >> average, not including minimization??) for a given lambda window?
> > > > >> http://pubs.acs.org/doi/abs/10.1021/jp102971x
> > > > >> (talking about page 10242 of article)
> > > > >> For 300 K, 1-2 KT is 0.596 - 1.192 Kcal/mol.
> > > > >> The variance (considering ensemble (not minimization values) dG
> > > values
> > > > >> for first window, lambd= 0 to lambda=0.05) is 0.0158. So it's one
> > > order
> > > > >> lower. This means I need to change dlambda and/or change the
> number of
> > > > >> steps after minimization?
> > > > >>
> > > > >> thanks,
> > > > >> Shyno
> > > > >>
> > > > >> --
> > > > >> Shyno Mathew
> > > > >> PhD student
> > > > >> Department of Chemical Engineering
> > > > >> Columbia University
> > > > >>
> > > > >>
> > > > >
> > > > >
> > > > > --
> > > > > Shyno Mathew
> > > > > PhD student
> > > > > Department of Chemical Engineering
> > > > > Columbia University
> > > > >
> > > >
> > > >
> > > >
> > > > --
> > > > Shyno Mathew
> > > > PhD student
> > > > Department of Chemical Engineering
> > > > Columbia University
> > > >
> > >
> >
> >
> >
> > --
> > Shyno Mathew
> > PhD student
> > Department of Chemical Engineering
> > Columbia University
> >
>

-- 
Shyno Mathew
PhD student
Department of Chemical Engineering
Columbia University

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