Gibbs Ensemble MCExamination of Java Code. Molecule Exchange

/**

* Performs a GEMC molecule-exchange trial

*/

private void trialExchange(Phase iPhase, Phase dPhase, Species species) {

Species.Agent iSpecies = species.getAgent(iPhase); //insertion-phase speciesAgent

Species.Agent dSpecies = species.getAgent(dPhase); //deletion-phase species Agent

double uNew, uOld;

if(dSpecies.nMolecules == 0) {return;} //no molecules to delete; trial is over

Molecule m = dSpecies.randomMolecule(); //select random molecule to delete

uOld = dPhase.potentialEnergy.currentValue(m); //get its contribution to energy

m.displaceTo(iPhase.randomPosition()); //place at random in insertion phase

uNew = iPhase.potentialEnergy.insertionValue(m); //get its new energy

if(uNew == Double.MAX_VALUE) { //overlap; reject

m.replace(); //put it back

return;

}

double bFactor = dSpecies.nMolecules/dPhase.volume()//acceptance probability

* iPhase.volume()/(iSpecies.nMolecules+1)

* Math.exp(-(uNew-uOld)/temperature);

if(bFactor > 1.0 || bFactor > rand.nextDouble()) { //accept

iPhase.addMolecule(m,iSpecies); //place molecule in phase

}

else { //reject

m.replace(); //put it back

}

}

public class IntegratorGEMC extends Integrator

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