void testCutoff14() {
System system;
VerletIntegrator integrator(0.01);
NonbondedForce* nonbonded = new NonbondedForce();
nonbonded->setNonbondedMethod(NonbondedForce::CutoffNonPeriodic);
for (int i = 0; i < 5; ++i) {
system.addParticle(1.0);
nonbonded->addParticle(0, 1.5, 0);
}
const double cutoff = 3.5;
nonbonded->setCutoffDistance(cutoff);
const double eps = 30.0;
nonbonded->setReactionFieldDielectric(eps);
vector<pair<int, int> > bonds;
bonds.push_back(pair<int, int>(0, 1));
bonds.push_back(pair<int, int>(1, 2));
bonds.push_back(pair<int, int>(2, 3));
bonds.push_back(pair<int, int>(3, 4));
nonbonded->createExceptionsFromBonds(bonds, 0.0, 0.0);
int first14, second14;
for (int i = 0; i < nonbonded->getNumExceptions(); i++) {
int particle1, particle2;
double chargeProd, sigma, epsilon;
nonbonded->getExceptionParameters(i, particle1, particle2, chargeProd, sigma, epsilon);
if ((particle1 == 0 && particle2 == 3) || (particle1 == 3 && particle2 == 0))
first14 = i;
if ((particle1 == 1 && particle2 == 4) || (particle1 == 4 && particle2 == 1))
second14 = i;
}
system.addForce(nonbonded);
Context context(system, integrator, platform);
vector<Vec3> positions(5);
positions[0] = Vec3(0, 0, 0);
positions[1] = Vec3(1, 0, 0);
positions[2] = Vec3(2, 0, 0);
positions[3] = Vec3(3, 0, 0);
positions[4] = Vec3(4, 0, 0);
for (int i = 1; i < 5; ++i) {
// Test LJ forces
nonbonded->setParticleParameters(0, 0, 1.5, 1);
for (int j = 1; j < 5; ++j)
nonbonded->setParticleParameters(j, 0, 1.5, 0);
nonbonded->setParticleParameters(i, 0, 1.5, 1);
nonbonded->setExceptionParameters(first14, 0, 3, 0, 1.5, i == 3 ? 0.5 : 0.0);
nonbonded->setExceptionParameters(second14, 1, 4, 0, 1.5, 0.0);
context.reinitialize();
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state.getForces();
double r = positions[i][0];
double x = 1.5/r;
double e = 1.0;
double force = 4.0*e*(12*std::pow(x, 12.0)-6*std::pow(x, 6.0))/r;
double energy = 4.0*e*(std::pow(x, 12.0)-std::pow(x, 6.0));
if (i == 3) {
force *= 0.5;
energy *= 0.5;
}
if (i < 3 || r > cutoff) {
force = 0;
energy = 0;
}
ASSERT_EQUAL_VEC(Vec3(-force, 0, 0), forces[0], TOL);
ASSERT_EQUAL_VEC(Vec3(force, 0, 0), forces[i], TOL);
ASSERT_EQUAL_TOL(energy, state.getPotentialEnergy(), TOL);
// Test Coulomb forces
const double q = 0.7;
nonbonded->setParticleParameters(0, q, 1.5, 0);
nonbonded->setParticleParameters(i, q, 1.5, 0);
nonbonded->setExceptionParameters(first14, 0, 3, i == 3 ? q*q/1.2 : 0, 1.5, 0);
nonbonded->setExceptionParameters(second14, 1, 4, 0, 1.5, 0);
context.reinitialize();
context.setPositions(positions);
state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces2 = state.getForces();
force = ONE_4PI_EPS0*q*q/(r*r);
energy = ONE_4PI_EPS0*q*q/r;
if (i == 3) {
force /= 1.2;
energy /= 1.2;
}
if (i < 3 || r > cutoff) {
force = 0;
energy = 0;
}
ASSERT_EQUAL_VEC(Vec3(-force, 0, 0), forces2[0], TOL);
ASSERT_EQUAL_VEC(Vec3(force, 0, 0), forces2[i], TOL);
ASSERT_EQUAL_TOL(energy, state.getPotentialEnergy(), TOL);
}
}
void testEnergyEthane(int applyBornRadiiScaling) {
ReferencePlatform platform;
const int numParticles = 8;
System system;
LangevinIntegrator integrator(0, 0.1, 0.01);
// harmonic bond
double C_HBondDistance = 0.1097;
double C_CBondDistance = 0.1504;
HarmonicBondForce* bonds = new HarmonicBondForce();
bonds->addBond(0, 1, C_HBondDistance, 0.0);
bonds->addBond(2, 1, C_HBondDistance, 0.0);
bonds->addBond(3, 1, C_HBondDistance, 0.0);
bonds->addBond(1, 4, C_CBondDistance, 0.0);
bonds->addBond(5, 4, C_HBondDistance, 0.0);
bonds->addBond(6, 4, C_HBondDistance, 0.0);
bonds->addBond(7, 4, C_HBondDistance, 0.0);
system.addForce(bonds);
double C_radius, C_gamma, C_charge, H_radius, H_gamma, H_charge;
int AM1_BCC = 1;
H_charge = -0.053;
C_charge = -3.0*H_charge;
if (AM1_BCC) {
C_radius = 0.180;
C_gamma = -0.2863;
H_radius = 0.125;
H_gamma = 0.2437;
}
else {
C_radius = 0.215;
C_gamma = -1.1087;
H_radius = 0.150;
H_gamma = 0.1237;
}
NonbondedForce* nonbonded = new NonbondedForce();
nonbonded->setNonbondedMethod(NonbondedForce::NoCutoff);
GBVIForce* forceField = new GBVIForce();
if (applyBornRadiiScaling) {
forceField->setBornRadiusScalingMethod(GBVIForce::QuinticSpline);
}
else {
forceField->setBornRadiusScalingMethod(GBVIForce::NoScaling);
}
for (int i = 0; i < numParticles; i++) {
system.addParticle(1.0);
forceField->addParticle(H_charge, H_radius, H_gamma);
nonbonded->addParticle( H_charge, H_radius, 0.0);
}
forceField->setParticleParameters(1, C_charge, C_radius, C_gamma);
forceField->setParticleParameters(4, C_charge, C_radius, C_gamma);
nonbonded->setParticleParameters( 1, C_charge, C_radius, 0.0);
nonbonded->setParticleParameters( 4, C_charge, C_radius, 0.0);
forceField->addBond(0, 1, C_HBondDistance);
forceField->addBond(2, 1, C_HBondDistance);
forceField->addBond(3, 1, C_HBondDistance);
forceField->addBond(1, 4, C_CBondDistance);
forceField->addBond(5, 4, C_HBondDistance);
forceField->addBond(6, 4, C_HBondDistance);
forceField->addBond(7, 4, C_HBondDistance);
std::vector<pair<int, int> > bondExceptions;
std::vector<double> bondDistances;
bondExceptions.push_back(pair<int, int>(0, 1));
bondDistances.push_back(C_HBondDistance);
bondExceptions.push_back(pair<int, int>(2, 1));
bondDistances.push_back(C_HBondDistance);
bondExceptions.push_back(pair<int, int>(3, 1));
bondDistances.push_back(C_HBondDistance);
bondExceptions.push_back(pair<int, int>(1, 4));
bondDistances.push_back(C_CBondDistance);
bondExceptions.push_back(pair<int, int>(5, 4));
bondDistances.push_back(C_HBondDistance);
bondExceptions.push_back(pair<int, int>(6, 4));
bondDistances.push_back(C_HBondDistance);
bondExceptions.push_back(pair<int, int>(7, 4));
bondDistances.push_back(C_HBondDistance);
nonbonded->createExceptionsFromBonds(bondExceptions, 0.0, 0.0);
system.addForce(forceField);
system.addForce(nonbonded);
Context context(system, integrator, platform);
vector<Vec3> positions(numParticles);
positions[0] = Vec3(0.5480, 1.7661, 0.0000);
positions[1] = Vec3(0.7286, 0.8978, 0.6468);
positions[2] = Vec3(0.4974, 0.0000, 0.0588);
positions[3] = Vec3(0.0000, 0.9459, 1.4666);
positions[4] = Vec3(2.1421, 0.8746, 1.1615);
positions[5] = Vec3(2.3239, 0.0050, 1.8065);
positions[6] = Vec3(2.8705, 0.8295, 0.3416);
positions[7] = Vec3(2.3722, 1.7711, 1.7518);
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
// Take a small step in the direction of the energy gradient.
double norm = 0.0;
double forceSum[3] = { 0.0, 0.0, 0.0 };
for (int i = 0; i < numParticles; ++i) {
Vec3 f = state.getForces()[i];
norm += f[0]*f[0] + f[1]*f[1] + f[2]*f[2];
forceSum[0] += f[0];
forceSum[1] += f[1];
forceSum[2] += f[2];
}
norm = std::sqrt(norm);
const double delta = 1e-4;
double step = delta/norm;
for (int i = 0; i < numParticles; ++i) {
Vec3 p = positions[i];
Vec3 f = state.getForces()[i];
positions[i] = Vec3(p[0]-f[0]*step, p[1]-f[1]*step, p[2]-f[2]*step);
}
context.setPositions(positions);
State state2 = context.getState(State::Energy);
// See whether the potential energy changed by the expected amount.
ASSERT_EQUAL_TOL(norm, (state2.getPotentialEnergy()-state.getPotentialEnergy())/delta, 0.01)
}
void testExclusionsAnd14() {
System system;
NonbondedForce* nonbonded = new NonbondedForce();
for (int i = 0; i < 5; ++i) {
system.addParticle(1.0);
nonbonded->addParticle(0, 1.5, 0);
}
vector<pair<int, int> > bonds;
bonds.push_back(pair<int, int>(0, 1));
bonds.push_back(pair<int, int>(1, 2));
bonds.push_back(pair<int, int>(2, 3));
bonds.push_back(pair<int, int>(3, 4));
nonbonded->createExceptionsFromBonds(bonds, 0.0, 0.0);
int first14, second14;
for (int i = 0; i < nonbonded->getNumExceptions(); i++) {
int particle1, particle2;
double chargeProd, sigma, epsilon;
nonbonded->getExceptionParameters(i, particle1, particle2, chargeProd, sigma, epsilon);
if ((particle1 == 0 && particle2 == 3) || (particle1 == 3 && particle2 == 0))
first14 = i;
if ((particle1 == 1 && particle2 == 4) || (particle1 == 4 && particle2 == 1))
second14 = i;
}
system.addForce(nonbonded);
VerletIntegrator integrator(0.01);
Context context(system, integrator, platform);
for (int i = 1; i < 5; ++i) {
// Test LJ forces
vector<Vec3> positions(5);
const double r = 1.0;
for (int j = 0; j < 5; ++j) {
nonbonded->setParticleParameters(j, 0, 1.5, 0);
positions[j] = Vec3(0, j, 0);
}
nonbonded->setParticleParameters(0, 0, 1.5, 1);
nonbonded->setParticleParameters(i, 0, 1.5, 1);
nonbonded->setExceptionParameters(first14, 0, 3, 0, 1.5, i == 3 ? 0.5 : 0.0);
nonbonded->setExceptionParameters(second14, 1, 4, 0, 1.5, 0.0);
positions[i] = Vec3(r, 0, 0);
context.reinitialize();
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state.getForces();
double x = 1.5/r;
double eps = 1.0;
double force = 4.0*eps*(12*std::pow(x, 12.0)-6*std::pow(x, 6.0))/r;
double energy = 4.0*eps*(std::pow(x, 12.0)-std::pow(x, 6.0));
if (i == 3) {
force *= 0.5;
energy *= 0.5;
}
if (i < 3) {
force = 0;
energy = 0;
}
ASSERT_EQUAL_VEC(Vec3(-force, 0, 0), forces[0], TOL);
ASSERT_EQUAL_VEC(Vec3(force, 0, 0), forces[i], TOL);
ASSERT_EQUAL_TOL(energy, state.getPotentialEnergy(), TOL);
// Test Coulomb forces
nonbonded->setParticleParameters(0, 2, 1.5, 0);
nonbonded->setParticleParameters(i, 2, 1.5, 0);
nonbonded->setExceptionParameters(first14, 0, 3, i == 3 ? 4/1.2 : 0, 1.5, 0);
nonbonded->setExceptionParameters(second14, 1, 4, 0, 1.5, 0);
context.reinitialize();
context.setPositions(positions);
state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces2 = state.getForces();
force = ONE_4PI_EPS0*4/(r*r);
energy = ONE_4PI_EPS0*4/r;
if (i == 3) {
force /= 1.2;
energy /= 1.2;
}
if (i < 3) {
force = 0;
energy = 0;
}
ASSERT_EQUAL_VEC(Vec3(-force, 0, 0), forces2[0], TOL);
ASSERT_EQUAL_VEC(Vec3(force, 0, 0), forces2[i], TOL);
ASSERT_EQUAL_TOL(energy, state.getPotentialEnergy(), TOL);
}
}
