std::vector<chemkit::Vector3> OplsTorsionCalculation::gradient() const
{
const chemkit::ForceFieldAtom *a = atom(0);
const chemkit::ForceFieldAtom *b = atom(1);
const chemkit::ForceFieldAtom *c = atom(2);
const chemkit::ForceFieldAtom *d = atom(3);
chemkit::Float v1 = parameter(0);
chemkit::Float v2 = parameter(1);
chemkit::Float v3 = parameter(2);
chemkit::Float phi = torsionAngleRadians(a, b, c, d);
// dE/dphi
chemkit::Float de_dphi = (1.0/2.0) * (-v1 * sin(phi) + 2.0 * v2 * sin(2.0 * phi) - 3.0 * v3 * sin(3.0 * phi));
std::vector<chemkit::Vector3> gradient = torsionAngleGradientRadians(a, b, c, d);
gradient[0] *= de_dphi;
gradient[1] *= de_dphi;
gradient[2] *= de_dphi;
gradient[3] *= de_dphi;
return gradient;
}
std::vector<chemkit::Vector3> UffTorsionCalculation::gradient() const
{
const chemkit::ForceFieldAtom *a = atom(0);
const chemkit::ForceFieldAtom *b = atom(1);
const chemkit::ForceFieldAtom *c = atom(2);
const chemkit::ForceFieldAtom *d = atom(3);
chemkit::Real V = parameter(0);
chemkit::Real n = parameter(1);
chemkit::Real phi0 = parameter(2);
chemkit::Real phi = torsionAngleRadians(a, b, c, d);
// dE/dphi
chemkit::Real de_dphi = 0.5 * V * n * cos(n * phi0) * sin(n * phi);
std::vector<chemkit::Vector3> gradient = torsionAngleGradientRadians(a, b, c, d);
gradient[0] *= de_dphi;
gradient[1] *= de_dphi;
gradient[2] *= de_dphi;
gradient[3] *= de_dphi;
return gradient;
}
std::vector<chemkit::Vector3> MmffTorsionCalculation::gradient() const
{
const MmffAtom *a = atom(0);
const MmffAtom *b = atom(1);
const MmffAtom *c = atom(2);
const MmffAtom *d = atom(3);
chemkit::Real phi = torsionAngleRadians(a, b, c, d);
chemkit::Real V1 = parameter(0);
chemkit::Real V2 = parameter(1);
chemkit::Real V3 = parameter(2);
// dE/dphi
chemkit::Real de_dphi = 0.5 * (-V1 * sin(phi) + 2 * V2 * sin(2 * phi) - 3 * V3 * sin(3 * phi));
std::vector<chemkit::Vector3> gradient = torsionAngleGradientRadians(a, b, c, d);
gradient[0] *= de_dphi;
gradient[1] *= de_dphi;
gradient[2] *= de_dphi;
gradient[3] *= de_dphi;
return gradient;
}
