| 36 |
|
* [1] Meineke, et al., J. Comp. Chem. 26, 252-271 (2005). |
| 37 |
|
* [2] Fennell & Gezelter, J. Chem. Phys. 124, 234104 (2006). |
| 38 |
|
* [3] Sun, Lin & Gezelter, J. Chem. Phys. 128, 24107 (2008). |
| 39 |
< |
* [4] Vardeman & Gezelter, in progress (2009). |
| 39 |
> |
* [4] Kuang & Gezelter, J. Chem. Phys. 133, 164101 (2010). |
| 40 |
> |
* [5] Vardeman, Stocker & Gezelter, J. Chem. Theory Comput. 7, 834 (2011). |
| 41 |
|
*/ |
| 42 |
|
|
| 43 |
+ |
#include "config.h" |
| 44 |
+ |
#include <cmath> |
| 45 |
+ |
|
| 46 |
|
#include "primitives/Torsion.hpp" |
| 47 |
|
|
| 48 |
|
namespace OpenMD { |
| 51 |
|
TorsionType *tt) : |
| 52 |
|
atom1_(atom1), atom2_(atom2), atom3_(atom3), atom4_(atom4), torsionType_(tt) { } |
| 53 |
|
|
| 54 |
< |
void Torsion::calcForce(RealType& angle) { |
| 54 |
> |
void Torsion::calcForce(RealType& angle, bool doParticlePot) { |
| 55 |
|
|
| 56 |
|
Vector3d pos1 = atom1_->getPos(); |
| 57 |
|
Vector3d pos2 = atom2_->getPos(); |
| 67 |
|
RealType rA = A.length(); |
| 68 |
|
Vector3d B = cross(r32, r43); |
| 69 |
|
RealType rB = B.length(); |
| 66 |
– |
Vector3d C = cross(r32, A); |
| 67 |
– |
RealType rC = C.length(); |
| 70 |
|
|
| 71 |
+ |
/* |
| 72 |
+ |
If either of the two cross product vectors is tiny, that means |
| 73 |
+ |
the three atoms involved are colinear, and the torsion angle is |
| 74 |
+ |
going to be undefined. The easiest check for this problem is |
| 75 |
+ |
to use the product of the two lengths. |
| 76 |
+ |
*/ |
| 77 |
+ |
if (rA * rB < OpenMD::epsilon) return; |
| 78 |
+ |
|
| 79 |
|
A.normalize(); |
| 80 |
< |
B.normalize(); |
| 71 |
< |
C.normalize(); |
| 80 |
> |
B.normalize(); |
| 81 |
|
|
| 82 |
|
// Calculate the sin and cos |
| 83 |
|
RealType cos_phi = dot(A, B) ; |
| 84 |
|
if (cos_phi > 1.0) cos_phi = 1.0; |
| 85 |
|
if (cos_phi < -1.0) cos_phi = -1.0; |
| 86 |
< |
|
| 86 |
> |
|
| 87 |
|
RealType dVdcosPhi; |
| 88 |
|
torsionType_->calcForce(cos_phi, potential_, dVdcosPhi); |
| 89 |
|
Vector3d f1 ; |
| 90 |
|
Vector3d f2 ; |
| 91 |
|
Vector3d f3 ; |
| 92 |
< |
|
| 92 |
> |
|
| 93 |
|
Vector3d dcosdA = (cos_phi * A - B) /rA; |
| 94 |
|
Vector3d dcosdB = (cos_phi * B - A) /rB; |
| 95 |
< |
|
| 95 |
> |
|
| 96 |
|
f1 = dVdcosPhi * cross(r32, dcosdA); |
| 97 |
|
f2 = dVdcosPhi * ( cross(r43, dcosdB) - cross(r21, dcosdA)); |
| 98 |
|
f3 = dVdcosPhi * cross(dcosdB, r32); |
| 101 |
|
atom2_->addFrc(f2 - f1); |
| 102 |
|
atom3_->addFrc(f3 - f2); |
| 103 |
|
atom4_->addFrc(-f3); |
| 104 |
< |
|
| 105 |
< |
atom1_->addParticlePot(potential_); |
| 106 |
< |
atom2_->addParticlePot(potential_); |
| 107 |
< |
atom3_->addParticlePot(potential_); |
| 108 |
< |
atom4_->addParticlePot(potential_); |
| 109 |
< |
|
| 110 |
< |
angle = acos(cos_phi) /M_PI * 180.0; |
| 111 |
< |
} |
| 112 |
< |
|
| 104 |
> |
|
| 105 |
> |
if (doParticlePot) { |
| 106 |
> |
atom1_->addParticlePot(potential_); |
| 107 |
> |
atom2_->addParticlePot(potential_); |
| 108 |
> |
atom3_->addParticlePot(potential_); |
| 109 |
> |
atom4_->addParticlePot(potential_); |
| 110 |
> |
} |
| 111 |
> |
|
| 112 |
> |
angle = acos(cos_phi) /M_PI * 180.0; |
| 113 |
> |
} |
| 114 |
|
} |
