public void Compute(Universe.Angle angle, Vector[] coords, ref double energy, ref Vector[] forces, ref MatrixByArr[,] hessian, double[,] pwfrc = null, double[,] pwspr = null)
{
double Ktheta = angle.Ktheta;
Ktheta = sprcstRgdbdy;
Ktheta = angle.Ktheta * scaleSpring;
double Theta0 = angle.Theta0;
double Kub = angle.Kub;
double S0 = angle.S0;
MindyAngle.Compute(coords, ref energy, ref forces, ref hessian, Ktheta, Theta0, Kub, S0, pwfrc, pwspr);
}
public void BuildHess4PwIntrAct(Universe.AtomPack info, Vector[] coords, out Pair <int, int>[] pwidxs, out PwIntrActInfo[] pwhessinfos)
{
Universe.Improper improper = (Universe.Improper)info;
double Kchi = improper.Kpsi;
int n = improper.n;
double delta = improper.psi0;
//Vector pos1 = coords[0]; // const Vector *pos1 = coords + angle->atom1;
//Vector pos2 = coords[1]; // const Vector *pos2 = coords + angle->atom2;
//Vector pos3 = coords[2]; // const Vector *pos3 = coords + angle->atom3;
//double a = (pos2-pos1).Dist;
//double b = (pos3-pos2).Dist;
//double c = (pos3-pos1).Dist;
//Pair<double,double> fij_kij = GetFijKij(a, b, c, Ktheta, Theta0);
//double fij = fij_kij.first;
//double kij = fij_kij.second;
/// A
/// / B
/// a .../. c /
/// \ / / \ /
/// \ / /\
/// \ / / \
/// b ..... d
///
/// a
/// |\ /
/// | \ /T
/// | \ ----- A ----+----
/// | \ /
/// | \ B
/// p l /
/// | \ \ /
/// |T \ \
/// | \ \
/// \ \
/// \\
/// d
///
/// A = (b-a) x (c-b)
/// B = (c-b) x (d-c)
/// (A x B) ⊥ (Δ adp)
/// p ∈ bc
/// T + ∠apd = π
///
/// V = K0 (T - T0)^2
/// F = dV/dT = 2 K0 (T - T0)
/// K = (d^2 V)/(d T^2) = 2 K0
/// return { dV/dl, (d^2 V)/(d l^2) }
Vector a = coords[0];
Vector b = coords[1];
Vector c = coords[2];
Vector d = coords[3];
Vector A = LinAlg.CrossProd(a - b, b - c);
Vector B = LinAlg.CrossProd(b - c, c - d);
Vector AxB = LinAlg.CrossProd(A, B);
double ad = (a - d).Dist;
Vector p = Geometry.Point4LinePlaneIntersect(a, d, a + A, b, c);
double ap = (a - p).Dist;
double pd = (p - d).Dist;
ValueTuple <double, double> fij_kij = MindyAngle.GetFijKij(ap, pd, ad, Kchi, delta, -1, +1, -1);
double fij = fij_kij.Item1;
double kij = fij_kij.Item2;
HDebug.Assert(coords.Length == 4);
pwidxs = new Pair <int, int> [1];
pwidxs[0] = new Pair <int, int>(0, 3);
pwhessinfos = new PwIntrActInfo[1];
pwhessinfos[0] = new PwIntrActInfo(kij, fij);
}