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CPHMD replica exhange criteria

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Top 10 Contributor
7 Posts
guangdianzi3 posted on 04-07-2010 9:27 PM

Hi, all

For replica exchange process in order to converge towards an equilibrium distribution, it is necessary to impose a detailed balance condition on the transition probability.

As the kinetic energy in Hamiltonion cancels out, the difference of total energy is in fact the difference of potential energy. REMD uses this potential energy difference to decide whether to change or not.

However, it seems like that in mmtsb tools, REMD still uses the the difference of potential energy which doesn't contain lambda. So will it influence the sampling since the Hamiltonion is supposed to be an extended one?

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Top 10 Contributor
26 Posts
why do you say it seems like the energy doesn't include the protonation state (lambda) ? If you print the charmm logfile then the energy used for exchange is the potential energy of the system.. ENER ENR: Eval# ENERgy Delta-E GRMS ENER INTERN: BONDs ANGLes UREY-b DIHEdrals IMPRopers ENER EXTERN: VDWaals ELEC HBONds ASP USER ENER PBEQ: PBnp PBelec GBEnr GSBP ENER PHMD: PHENr PHKInetic ---------- --------- --------- --------- --------- --------- ENER> 0 >>> -136.88461<<< 3.60207 12.01345 2.76553 1.97304 1.47572 ENER EXTERN> -0.46628 -91.82251 0.00000 1.21355 0.00000 ENER PBEQ> 0.00000 0.00000 -106.38784 0.00000 ENER PHMD> 38.74866 0.78423 ---------- --------- --------- --------- --------- --------- when you use phmd in charmm this energy contains ALL of the potential energy including the "ENER PHMD" term ENER PHMD is just printed out separately for your convenience.
Top 10 Contributor
7 Posts

I get it. Thank your for reply

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