public override void CalculateForceField(ParticleEnsemble ensemble)
{
// variable declarations
double posXi, posYi;
double posXj, posYj;
double ijSeparation = 0.0, LJforce = 0.0, PotentialEnergy = 0.0;
// variable initializations
int BoxHeight = ensemble.BoxHeight;
int BoxWidth = ensemble.BoxWidth;
double MaxForce = ensemble.MaxForceThreshold;
double MinForce = -1.0 * (ensemble.MaxForceThreshold);
DPVector zero = new DPVector(0, 0);
// initialize vectors holding forces
for (int i = 0; i < ensemble.NumberOfParticles; ++i)
{
LJforces[i] = zero;
}
ensemble.ResetAllParticlesNotWithinRange();
for (int i = 0; i < ensemble.NumberOfParticles; ++i)
{
Particle particlei = ensemble.GetParticle(i);
for (int j = (i + 1); j < ensemble.NumberOfParticles; ++j)
{
Particle particlej = ensemble.GetParticle(j);
// get the interparticle separation distances
ijSeparation = ensemble.GetInterParticleSeparation(i, j);
double LJgradientTermA = particlei.ParticleType.LJgradientTermA[particlej.TypeID];
double LJgradientTermB = particlei.ParticleType.LJgradientTermB[particlej.TypeID];
// update the radial distribution function
double cutoffDistance = particlei.ParticleType.MinimumDistance[particlej.TypeID]; // MinimumDistance[i, j];
if (ijSeparation < cutoffDistance)
{
// for each particle, change the appropriate element of the setWithinRangeOfAnotherParticle vector to true
posXi = particlei.Position.X;
posYi = particlei.Position.Y;
posXj = particlej.Position.X;
posYj = particlej.Position.Y;
LJforce = (posXj - posXi) * (LJgradientTermA / Math.Pow(ijSeparation, 13.0) + LJgradientTermB / Math.Pow(ijSeparation, 7.0)) / ijSeparation;
if (Math.Abs(LJforce) > MaxForce || Math.Abs(LJforce) < MinForce)
{
// error check for real-time stability...
LJforce = 0.0;
}
else if(double.IsNaN(LJforce) || double.IsInfinity(LJforce))
{
// error check for real-time stability...
LJforce = 0.0;
}
LJforces[i].X += LJforce;
LJforces[j].X += -1.0 * LJforce;
LJforce = (posYj - posYi) * (LJgradientTermA / Math.Pow(ijSeparation, 13.0) + LJgradientTermB / Math.Pow(ijSeparation, 7.0)) / ijSeparation;
if (Math.Abs(LJforce) > MaxForce || Math.Abs(LJforce) < MinForce)
{
// error check for real-time stability...
LJforce = 0.0;
}
else if (double.IsNaN(LJforce) || double.IsInfinity(LJforce))
{
// error check for real-time stability...
LJforce = 0.0;
}
LJforces[i].Y += LJforce;
LJforces[j].Y += -1.0 * LJforce;
ensemble.SetParticlesWithinRange(i, j);
ensemble.SetParticlesWithinRange(j, i);
}
//else
//{
// ensemble.SetParticlesNotWithinRange(i, j);
//ensemble.SetParticlesNotWithinRange(j, i);
//}
}
}
// set the forces in the Particle Ensemble Object
ensemble.AddForces(LJforces);
// set the potential energy
ensemble.AddPotentialEnergy(PotentialEnergy);
}
