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/* |
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* Copyright (c) 2005 The University of Notre Dame. All Rights Reserved. |
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* |
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* The University of Notre Dame grants you ("Licensee") a |
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* non-exclusive, royalty free, license to use, modify and |
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* redistribute this software in source and binary code form, provided |
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* that the following conditions are met: |
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* |
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* 1. Acknowledgement of the program authors must be made in any |
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* publication of scientific results based in part on use of the |
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* program. An acceptable form of acknowledgement is citation of |
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* the article in which the program was described (Matthew |
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* A. Meineke, Charles F. Vardeman II, Teng Lin, Christopher |
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* J. Fennell and J. Daniel Gezelter, "OOPSE: An Object-Oriented |
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* Parallel Simulation Engine for Molecular Dynamics," |
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* J. Comput. Chem. 26, pp. 252-271 (2005)) |
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* |
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* 2. Redistributions of source code must retain the above copyright |
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* notice, this list of conditions and the following disclaimer. |
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* |
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* 3. Redistributions in binary form must reproduce the above copyright |
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* notice, this list of conditions and the following disclaimer in the |
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* documentation and/or other materials provided with the |
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* distribution. |
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* |
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* This software is provided "AS IS," without a warranty of any |
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* kind. All express or implied conditions, representations and |
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* warranties, including any implied warranty of merchantability, |
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* fitness for a particular purpose or non-infringement, are hereby |
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* excluded. The University of Notre Dame and its licensors shall not |
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* be liable for any damages suffered by licensee as a result of |
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* using, modifying or distributing the software or its |
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* derivatives. In no event will the University of Notre Dame or its |
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* licensors be liable for any lost revenue, profit or data, or for |
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* direct, indirect, special, consequential, incidental or punitive |
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* damages, however caused and regardless of the theory of liability, |
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* arising out of the use of or inability to use software, even if the |
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* University of Notre Dame has been advised of the possibility of |
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* such damages. |
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*/ |
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|
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#include "primitives/Bend.hpp" |
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|
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namespace oopse { |
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|
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/**@todo still a lot left to improve*/ |
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void Bend::calcForce() { |
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Vector3d pos1 = atom1_->getPos(); |
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Vector3d pos2 = atom2_->getPos(); |
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Vector3d pos3 = atom3_->getPos(); |
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|
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Vector3d r21 = pos1 - pos2; |
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double d21 = r21.length(); |
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|
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double d21inv = 1.0 / d21; |
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|
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Vector3d r23 = pos3 - pos2; |
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double d23 = r23.length(); |
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|
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double d23inv = 1.0 / d23; |
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|
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double cosTheta = dot(r21, r23) / (d21 * d23); |
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|
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//check roundoff |
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if (cosTheta > 1.0) { |
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cosTheta = 1.0; |
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} else if (cosTheta < -1.0) { |
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cosTheta = -1.0; |
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} |
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|
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double theta = acos(cosTheta); |
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|
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double dVdTheta; |
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|
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bendType_->calcForce(theta, potential_, dVdTheta); |
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|
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double sinTheta = sqrt(1.0 - cosTheta * cosTheta); |
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|
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if (fabs(sinTheta) < 1.0E-6) { |
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sinTheta = 1.0E-6; |
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} |
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|
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double commonFactor1 = dVdTheta / sinTheta * d21inv; |
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double commonFactor2 = dVdTheta / sinTheta * d23inv; |
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|
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Vector3d force1 = commonFactor1 * (r23 * d23inv - r21*d21inv*cosTheta); |
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Vector3d force3 = commonFactor2 * (r21 * d21inv - r23*d23inv*cosTheta); |
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|
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//total force in current bend is zero |
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Vector3d force2 = force1 + force3; |
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force2 *= -1.0; |
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|
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atom1_->addFrc(force1); |
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atom2_->addFrc(force2); |
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atom3_->addFrc(force3); |
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} |
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|
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} //end namespace oopse |
