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root/group/trunk/OOPSE/libmdtools/Thermo.cpp
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Comparing trunk/OOPSE/libmdtools/Thermo.cpp (file contents):
Revision 458 by gezelter, Fri Apr 4 19:47:19 2003 UTC vs.
Revision 483 by gezelter, Wed Apr 9 04:06:43 2003 UTC

# Line 134 | Line 134 | double Thermo::getPressure(){
134    return temperature;
135   }
136  
137 < double Thermo::getPressure(){
138 <  // returns pressure in units amu*fs^-2*Ang^-1
137 > double Thermo::getPressure() {
138 >  // returns the pressure in units of atm
139 >  // Relies on the calculation of the full molecular pressure tensor
140 >  
141 >  const double p_convert = 1.63882576e8;
142 >  double press[9];
143 >  double pressure;
144 >
145 >  this->getPressureTensor(press);
146 >
147 >  pressure = p_convert * (press[0] + press[4] + press[8]) / 3.0;
148 >
149 >  return pressure;
150 > }
151 >
152 >
153 > void Thermo::getPressureTensor(double press[9]){
154 >  // returns pressure tensor in units amu*fs^-2*Ang^-1
155    // routine derived via viral theorem description in:
156    // Paci, E. and Marchi, M. J.Phys.Chem. 1996, 100, 4314-4322
157  
158 <  return 0.0;
158 >  const double e_convert = 4.184e-4;
159 >
160 >  double molmass, volume;
161 >  double vcom[3];
162 >  double p_local[9], p_global[9];
163 >  double theBox[3];
164 >  double* tau;
165 >  int i, nMols;
166 >  Molecule* molecules;
167 >
168 >  nMols = entry_plug->n_mol;
169 >  molecules = entry_plug->molecules;
170 >  tau = entry_plug->tau;
171 >
172 >  // use velocities of molecular centers of mass and molecular masses:
173 >  for (i=0; i < 9; i++) {    
174 >    p_local[i] = 0.0;
175 >    p_global[i] = 0.0;
176 >  }
177 >
178 >  for (i=0; i < nMols; i++) {
179 >    molmass = molecules[i].getCOMvel(vcom);
180 >
181 >    p_local[0] += molmass * (vcom[0] * vcom[0]);
182 >    p_local[1] += molmass * (vcom[0] * vcom[1]);
183 >    p_local[2] += molmass * (vcom[0] * vcom[2]);
184 >    p_local[3] += molmass * (vcom[1] * vcom[0]);
185 >    p_local[4] += molmass * (vcom[1] * vcom[1]);
186 >    p_local[5] += molmass * (vcom[1] * vcom[2]);
187 >    p_local[6] += molmass * (vcom[2] * vcom[0]);
188 >    p_local[7] += molmass * (vcom[2] * vcom[1]);
189 >    p_local[8] += molmass * (vcom[2] * vcom[2]);
190 >  }
191 >
192 >  // Get total for entire system from MPI.
193 >
194 > #ifdef IS_MPI
195 >  MPI_Allreduce(p_local,p_global,9,MPI_DOUBLE, MPI_SUM, MPI_COMM_WORLD);
196 > #else
197 >  for (i=0; i<9; i++) {
198 >    p_global[i] = p_local[i];
199 >  }
200 > #endif // is_mpi
201 >
202 >  entry_plug->getBox(theBox);
203 >
204 >  volume = theBox[0] * theBox[1] * theBox[2];
205 >
206 >  for(i=0; i<9; i++) {
207 >    press[i] = (p_global[i] - tau[i]*e_convert) / volume;
208 >  }
209   }
210  
211   void Thermo::velocitize() {

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