| 1 |
/* |
| 2 |
* Copyright (C) 2000-2004 Object Oriented Parallel Simulation Engine (OOPSE) project |
| 3 |
* |
| 4 |
* Contact: oopse@oopse.org |
| 5 |
* |
| 6 |
* This program is free software; you can redistribute it and/or |
| 7 |
* modify it under the terms of the GNU Lesser General Public License |
| 8 |
* as published by the Free Software Foundation; either version 2.1 |
| 9 |
* of the License, or (at your option) any later version. |
| 10 |
* All we ask is that proper credit is given for our work, which includes |
| 11 |
* - but is not limited to - adding the above copyright notice to the beginning |
| 12 |
* of your source code files, and to any copyright notice that you may distribute |
| 13 |
* with programs based on this work. |
| 14 |
* |
| 15 |
* This program is distributed in the hope that it will be useful, |
| 16 |
* but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 17 |
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 18 |
* GNU Lesser General Public License for more details. |
| 19 |
* |
| 20 |
* You should have received a copy of the GNU Lesser General Public License |
| 21 |
* along with this program; if not, write to the Free Software |
| 22 |
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 23 |
* |
| 24 |
*/ |
| 25 |
|
| 26 |
#include "types/CharmmTorsionType.hpp" |
| 27 |
|
| 28 |
namespace oopse { |
| 29 |
|
| 30 |
void CharmmTorsionType::calcForce(double cosPhi, double sinPhi, double& V, double& dVdPhi) { |
| 31 |
V = 0; |
| 32 |
dVdPhi = 0; |
| 33 |
double phi = -atan2(sinPhi, cosPhi); |
| 34 |
|
| 35 |
std::vector<CharmmTorsionParameter>::iterator i; |
| 36 |
for (i = parameter_.begin(); i != parameter_.end(); ++i) { |
| 37 |
double kchi= i->kchi; |
| 38 |
int n = i->n; |
| 39 |
double delta = i->delta; |
| 40 |
|
| 41 |
if (n == 0) { |
| 42 |
//if periodicity is equal to 0, use harmonic form |
| 43 |
double diff = phi - delta; |
| 44 |
|
| 45 |
if (diff < -OOPSEConstant::PI) { |
| 46 |
diff += OOPSEConstant::TWOPI; |
| 47 |
} else if (diff > OOPSEConstant::PI) { |
| 48 |
diff -= OOPSEConstant::TWOPI; |
| 49 |
} |
| 50 |
|
| 51 |
V += kchi * diff * diff; |
| 52 |
dVdPhi += 2.0 * kchi * diff; |
| 53 |
|
| 54 |
} else { |
| 55 |
//use normal cos form if periodicity is greater than 0 |
| 56 |
V += kchi * (1 + cos(n * phi + delta)); |
| 57 |
dVdPhi += -n * kchi * sin(n * phi + delta); |
| 58 |
} |
| 59 |
} |
| 60 |
} |
| 61 |
|
| 62 |
} //end namespace oopse |
