| 63 |
|
RealType rA = A.length(); |
| 64 |
|
Vector3d B = cross(r32, r43); |
| 65 |
|
RealType rB = B.length(); |
| 66 |
– |
Vector3d C = cross(r32, A); |
| 67 |
– |
RealType rC = C.length(); |
| 66 |
|
|
| 67 |
+ |
/* |
| 68 |
+ |
If either of the two cross product vectors is tiny, that means |
| 69 |
+ |
the three atoms involved are colinear, and the torsion angle is |
| 70 |
+ |
going to be undefined. The easiest check for this problem is |
| 71 |
+ |
to use the product of the two lengths. |
| 72 |
+ |
*/ |
| 73 |
+ |
if (rA * rB < OpenMD::epsilon) return; |
| 74 |
+ |
|
| 75 |
|
A.normalize(); |
| 76 |
< |
B.normalize(); |
| 71 |
< |
C.normalize(); |
| 76 |
> |
B.normalize(); |
| 77 |
|
|
| 78 |
|
// Calculate the sin and cos |
| 79 |
|
RealType cos_phi = dot(A, B) ; |
| 80 |
|
if (cos_phi > 1.0) cos_phi = 1.0; |
| 81 |
|
if (cos_phi < -1.0) cos_phi = -1.0; |
| 82 |
< |
|
| 82 |
> |
|
| 83 |
|
RealType dVdcosPhi; |
| 84 |
|
torsionType_->calcForce(cos_phi, potential_, dVdcosPhi); |
| 85 |
|
Vector3d f1 ; |
| 86 |
|
Vector3d f2 ; |
| 87 |
|
Vector3d f3 ; |
| 88 |
< |
|
| 88 |
> |
|
| 89 |
|
Vector3d dcosdA = (cos_phi * A - B) /rA; |
| 90 |
|
Vector3d dcosdB = (cos_phi * B - A) /rB; |
| 91 |
< |
|
| 91 |
> |
|
| 92 |
|
f1 = dVdcosPhi * cross(r32, dcosdA); |
| 93 |
|
f2 = dVdcosPhi * ( cross(r43, dcosdB) - cross(r21, dcosdA)); |
| 94 |
|
f3 = dVdcosPhi * cross(dcosdB, r32); |
| 97 |
|
atom2_->addFrc(f2 - f1); |
| 98 |
|
atom3_->addFrc(f3 - f2); |
| 99 |
|
atom4_->addFrc(-f3); |
| 100 |
< |
|
| 100 |
> |
|
| 101 |
|
atom1_->addParticlePot(potential_); |
| 102 |
|
atom2_->addParticlePot(potential_); |
| 103 |
|
atom3_->addParticlePot(potential_); |
| 104 |
|
atom4_->addParticlePot(potential_); |
| 105 |
< |
|
| 106 |
< |
angle = acos(cos_phi) /M_PI * 180.0; |
| 107 |
< |
} |
| 103 |
< |
|
| 105 |
> |
|
| 106 |
> |
angle = acos(cos_phi) /M_PI * 180.0; |
| 107 |
> |
} |
| 108 |
|
} |
