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root/group/trunk/OOPSE/libmdtools/Thermo.cpp
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Comparing trunk/OOPSE/libmdtools/Thermo.cpp (file contents):
Revision 479 by chuckv, Tue Apr 8 15:20:44 2003 UTC vs.
Revision 484 by gezelter, Wed Apr 9 13:59:35 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::getEnthalpy() {
138 >
139 >  const double e_convert = 4.184E-4; // convert kcal/mol -> (amu A^2)/fs^2
140 >  double u, p, v;
141 >  double press[9];
142 >
143 >  u = this->getTotalE();
144 >
145 >  this->getPressureTensor(press);
146 >  p = (press[0] + press[4] + press[8]) / 3.0;
147 >
148 >  v = this->getVolume();
149 >
150 >  return (u + (p*v)/e_convert);
151 > }
152 >
153 > double Thermo::getVolume() {
154 >  double theBox[3];
155 >
156 >  entry_plug->getBox(theBox);
157 >  return (theBox[0] * theBox[1] * theBox[2]);
158 > }
159 >
160 > double Thermo::getPressure() {
161 >  // returns the pressure in units of atm
162 >  // Relies on the calculation of the full molecular pressure tensor
163 >  
164 >  const double p_convert = 1.63882576e8;
165 >  double press[9];
166 >  double pressure;
167 >
168 >  this->getPressureTensor(press);
169 >
170 >  pressure = p_convert * (press[0] + press[4] + press[8]) / 3.0;
171 >
172 >  return pressure;
173 > }
174 >
175 >
176 > void Thermo::getPressureTensor(double press[9]){
177 >  // returns pressure tensor in units amu*fs^-2*Ang^-1
178    // routine derived via viral theorem description in:
179    // Paci, E. and Marchi, M. J.Phys.Chem. 1996, 100, 4314-4322
180  
181    const double e_convert = 4.184e-4;
182 <  const double p_convert = 1.63882576e8;
183 <  double molmass;
182 >
183 >  double molmass, volume;
184    double vcom[3];
185 <  double p_local, p_sum, p_mol, virial;
185 >  double p_local[9], p_global[9];
186    double theBox[3];
187    double* tau;
188    int i, nMols;
# Line 154 | Line 193 | double Thermo::getPressure(){
193    tau = entry_plug->tau;
194  
195    // use velocities of molecular centers of mass and molecular masses:
196 <  p_local = 0.0;
196 >  for (i=0; i < 9; i++) {    
197 >    p_local[i] = 0.0;
198 >    p_global[i] = 0.0;
199 >  }
200  
201    for (i=0; i < nMols; i++) {
202      molmass = molecules[i].getCOMvel(vcom);
203 <    p_local += (vcom[0]*vcom[0] + vcom[1]*vcom[1] + vcom[2]*vcom[2]) * molmass;
203 >
204 >    p_local[0] += molmass * (vcom[0] * vcom[0]);
205 >    p_local[1] += molmass * (vcom[0] * vcom[1]);
206 >    p_local[2] += molmass * (vcom[0] * vcom[2]);
207 >    p_local[3] += molmass * (vcom[1] * vcom[0]);
208 >    p_local[4] += molmass * (vcom[1] * vcom[1]);
209 >    p_local[5] += molmass * (vcom[1] * vcom[2]);
210 >    p_local[6] += molmass * (vcom[2] * vcom[0]);
211 >    p_local[7] += molmass * (vcom[2] * vcom[1]);
212 >    p_local[8] += molmass * (vcom[2] * vcom[2]);
213    }
214  
215    // Get total for entire system from MPI.
216  
217   #ifdef IS_MPI
218 <  MPI_Allreduce(&p_local,&p_sum,1,MPI_DOUBLE, MPI_SUM, MPI_COMM_WORLD);
218 >  MPI_Allreduce(p_local,p_global,9,MPI_DOUBLE, MPI_SUM, MPI_COMM_WORLD);
219   #else
220 <  p_sum = p_local;
220 >  for (i=0; i<9; i++) {
221 >    p_global[i] = p_local[i];
222 >  }
223   #endif // is_mpi
224  
172  virial = tau[0] + tau[4] + tau[8];
225    entry_plug->getBox(theBox);
226  
227 <  p_mol = p_convert * (p_sum - virial*e_convert) /
176 <    (3.0 * theBox[0] * theBox[1]* theBox[2]);
227 >  volume = theBox[0] * theBox[1] * theBox[2];
228  
229 <  return p_mol;
229 >  for(i=0; i<9; i++) {
230 >    press[i] = (p_global[i] - tau[i]*e_convert) / volume;
231 >  }
232   }
233  
234   void Thermo::velocitize() {

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