// calculates and adds its forces to the current forces of the force field
void MMFF94OutOfPlaneBend::updateForces()
{
const double FC = K0 * 2. * RADIAN_TO_DEGREE * RADIAN_TO_DEGREE;
bool us = getForceField()->getUseSelection();
//////////////////////////////////////////////////////////////////
// ids of the non-central atoms for the three runs per out of plane bend:
vector<vector<Position> > atom_ids;
// Atom i:
vector<Position> temp;
temp.push_back(0);
temp.push_back(0);
temp.push_back(1);
atom_ids.push_back(temp);
// Atom k:
temp.clear();
temp.push_back(1);
temp.push_back(2);
temp.push_back(2);
atom_ids.push_back(temp);
// Atom l:
temp.clear();
temp.push_back(2);
temp.push_back(1);
temp.push_back(0);
atom_ids.push_back(temp);
////////////////////////////////////////////////////////////////////////
// all calculations below have to be performed at double precision
// otherwise the results are far off, especially for small wilson angles
//
// temp variables:
double length;
TVector3<double> delta;
// the three atoms bound to the central atom (for the actual plane bend)
vector<Atom*> partners(3);
// lenght of the vectors from the central atom to outer atoms:
vector<double> lengths(3);
// normalized bond vectors from central atom to outer atoms:
vector<TVector3<double> > nbv(3);
// index of the individual atoms in partners and nbv:
Position pi, pk, pl;
// normal vectors of the three planes:
TVector3<double> an, bn, cn;
for (Position t = 0; t < bends_.size(); t++)
{
// the current bend
const OutOfPlaneBend& bend = bends_[t];
Atom& ta1 = *bend.i->ptr;
Atom& ta2 = *bend.j->ptr;
Atom& ta3 = *bend.k->ptr;
Atom& ta4 = *bend.l->ptr;
// if using selection and no atom is selected: ignore this bend:
if (us && !ta1.isSelected() &&
!ta2.isSelected() &&
!ta3.isSelected() &&
!ta4.isSelected())
{
continue;
}
// non central atoms for this bend:
partners[0] = &ta1;
partners[1] = &ta3;
partners[2] = &ta4;
Atom& center_atom = ta2;
// abort for this bend if two atoms have the same position:
bool error = false;
// calculate normalized bond vectors from central atom to outer atoms:
for (Position p = 0; p < 3; p++)
{
// transformation from single to double precision:
delta.x = partners[p]->getPosition().x - center_atom.getPosition().x;
delta.y = partners[p]->getPosition().y - center_atom.getPosition().y;
delta.z = partners[p]->getPosition().z - center_atom.getPosition().z;
length = delta.getLength();
if (Maths::isZero(length))
{
error = true;
break;
}
// normalize the bond vector:
delta /= length;
// store the normalized bond vector:
nbv[p] = delta;
// store length of this bond:
lengths[p] = length;
}
// abort if any bond lenght equals zero
if (error) continue;
// three runs per OOP:
for (Position run = 0; run < 3; run++)
{
// position of the individual atoms in partners[] and nbv[]
pi = atom_ids[0][run];
pk = atom_ids[1][run];
pl = atom_ids[2][run];
Atom& i = *partners[pi];
Atom& k = *partners[pk];
Atom& l = *partners[pl];
// normalized vectors from central atom to outer atoms:
const TVector3<double>& ji = nbv[pi];
const TVector3<double>& jk = nbv[pk];
const TVector3<double>& jl = nbv[pl];
const double& length_ji = lengths[pi];
const double& length_jk = lengths[pk];
const double& length_jl = lengths[pl];
// the normal vectors of the three planes:
an = ji % jk;
bn = jk % jl;
cn = jl % ji;
// Bond angle ji to jk
const double cos_theta = ji * jk;
const double theta = acos(cos_theta);
// If theta equals 180 degree or 0 degree
if (Maths::isZero(theta) ||
Maths::isZero(fabs(theta - Constants::PI)))
{
continue;
}
const double sin_theta = sin(theta);
const double sin_dl = an * jl / sin_theta;
// the wilson angle:
const double dl = asin(sin_dl);
// In case: wilson angle equals 0 or 180 degree: do nothing
if (Maths::isZero(dl) ||
Maths::isZero(fabs(dl - Constants::PI)))
{
continue;
}
const double cos_dl = cos(dl);
// if wilson angle equal 90 degree: abort
if (cos_dl < 0.0001)
{
continue;
}
// scaling factor for all forces:
// wilson K0 * this_bend_constant * wilson_angle * DEGREE_TO_RADIAN * DEGREE_TO_RADIAN
double c1 = -dl * FC * bend.k_oop * FORCES_FACTOR * Constants::JOULE_PER_CAL;
double tmp = cos_dl / c1;
/*
Log.precision(30);
Log.error() << "bond " << theta << std::endl;
Log.error() << "wilson " << dl << std::endl;
Log.error() << "tan_dl " << tan_dl << std::endl;
Log.error() << "cdst " << cdst << std::endl;
Log.error() << "tdst " << tdst << std::endl;
Log.error() << "c1 " << c1 << std::endl;
Log.error() << "abc " << an << bn << cn << std::endl << std::endl << std::endl << std::endl;
*/
const TVector3<double> d_l = ((an / sin_theta - jl * sin_dl) / length_jl) / tmp;
const TVector3<double> d_i = (((bn + (((-ji + jk * cos_theta) * sin_dl) / sin_theta)) / length_ji) / tmp) / sin_theta;
const TVector3<double> d_k = (((cn + (((-jk + ji * cos_theta) * sin_dl) / sin_theta)) / length_jk) / tmp) / sin_theta;
if (!us || i.isSelected()) AddDV3_(i.getForce(), d_i);
if (!us || k.isSelected()) AddDV3_(k.getForce(), d_k);
if (!us || l.isSelected()) AddDV3_(l.getForce(), d_l);
if (!us || center_atom.isSelected()) AddDV3_(center_atom.getForce(), -(d_i + d_k + d_l));
#ifdef BALL_MMFF94_TEST
getForceField()->error() << std::endl
<< i.getName() << " " << d_i << std::endl
<< center_atom.getName() << " " << -(d_i +d_k + d_l) << std::endl
<< k.getName() << " " << d_k << std::endl
<< l.getName() << " " << d_l << std::endl;
#endif
}
}
}
