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tim |
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/* |
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* Copyright (C) 2000-2004 Object Oriented Parallel Simulation Engine (OOPSE) project |
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* |
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* Contact: oopse@oopse.org |
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* |
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* This program is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public License |
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* as published by the Free Software Foundation; either version 2.1 |
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* of the License, or (at your option) any later version. |
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* All we ask is that proper credit is given for our work, which includes |
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* - but is not limited to - adding the above copyright notice to the beginning |
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* of your source code files, and to any copyright notice that you may distribute |
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* with programs based on this work. |
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* |
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* This program is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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* GNU Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public License |
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* along with this program; if not, write to the Free Software |
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
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* |
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*/ |
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#include "integrators/Velocitizer.hpp" |
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namespace oopse { |
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void Velocitizer::velocitize(double temperature) { |
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Vector3d aVel; |
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Vector3d aJ; |
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Mat3x3d I; |
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int l; |
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int m; |
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int n; // velocity randomizer loop counts |
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Vector3d vdrift; |
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double vbar; |
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const double kb = 8.31451e - 7; // kb in amu, angstroms, fs, etc. |
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double av2; |
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double kebar; |
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std::vector<Molecule *>::iterator i; |
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std::vector<StuntDouble *>::iterator j; |
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Molecule * mol; |
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StuntDouble * integrableObject; |
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gaussianSPRNG gaussStream(info_->getSeed()); |
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kebar = kb * temperature * info_->getNdfRaw() / (2.0 * info_->getNdf()); |
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for( mol = info_->beginMolecule(i); mol != NULL; |
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mol = info_->nextMolecule(i) ) { |
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for( integrableObject = mol->beginIntegrableObject(j); |
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integrableObject != NULL; |
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integrableObject = mol->nextIntegrableObject(j) ) { |
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// uses equipartition theory to solve for vbar in angstrom/fs |
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av2 = 2.0 * kebar / integrableObject->getMass(); |
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vbar = sqrt(av2); |
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// picks random velocities from a gaussian distribution |
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// centered on vbar |
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for( int k = 0; k < 3; k++ ) { |
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aVel[k] = vbar * gaussStream.getGaussian(); |
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} |
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integrableObject->setVel(aVel); |
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if (integrableObject->isDirectional()) { |
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I = integrableObject->getI(); |
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if (integrableObject->isLinear()) { |
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l = integrableObject->linearAxis(); |
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m = (l + 1) % 3; |
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n = (l + 2) % 3; |
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aJ[l] = 0.0; |
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vbar = sqrt(2.0 * kebar * I(m, m)); |
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aJ[m] = vbar * gaussStream.getGaussian(); |
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vbar = sqrt(2.0 * kebar * I(n, n)); |
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aJ[n] = vbar * gaussStream.getGaussian(); |
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} else { |
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for( int k = 0; k < 3; k++ ) { |
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vbar = sqrt(2.0 * kebar * I(k, k)); |
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aJ[k] = vbar * gaussStream.getGaussian(); |
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} |
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} // else isLinear |
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integrableObject->setJ(aJ); |
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} //isDirectional |
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} |
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} //end for (mol = beginMolecule(i); ...) |
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// Get the Center of Mass drift velocity. |
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vdrift = info_->getComVel(); |
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removeComDrift(vdrift); |
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} |
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void Velocitizer::removeComDrift(const Vector3d& vdrift) { |
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std::vector<Molecule *>::iterator i; |
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std::vector<StuntDouble *>::iterator j; |
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Molecule * mol; |
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StuntDouble * integrableObject; |
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// Corrects for the center of mass drift. |
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// sums all the momentum and divides by total mass. |
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for( mol = info_->beginMolecule(i); mol != NULL; |
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mol = info_->nextMolecule(i) ) { |
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for( integrableObject = mol->beginIntegrableObject(j); |
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integrableObject != NULL; |
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integrableObject = mol->nextIntegrableObject(j) ) { |
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integrableObject->setVel(integrableObject->getVel() - vdrift); |
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} |
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} |
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} |
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} |
