[gmx-users] TIP3P versus SPC?
Michael Shirts
mrshirts at stanford.edu
Tue Feb 18 03:17:24 CET 2003
Hi, all - I was just wondering about the differences of implementation of
TIP3P and SPC in GROMACS. I get a couple of odd things - below are outputs of
g_energy from two simulations, identical conditions except that one has TIP3P
and the other has SPC. PME, rlist = rcoulomb = 1.15, Switched VdW 0.9-1.1,
dispersion correction, 900 molecules, Nose-Hoover, Parrinello-Rahman.
The densities remain close to the experimental values, but the coulombic
energy for TIP3P is 20x that of SPC. Do you have any idea why this is the
case? It just seems rather odd that this differece in coulombic energy should
exist without there being other large differences in other properties. . .
Thanks,
Michael Shirts
Pande Group
Chemistry Department
Stanford University
SPC with PME
LJ (SR) 6464.53 259.014 259.007 0.00642346 6.42347
Disper. corr. -162.668 1.73525 1.73521 -3.73529e-05 -0.0373529
Coulomb (SR) -41653.8 560.793 560.781 -0.0128294 -12.8294
Coulomb (LR) -2074.37 11.5334 11.5334 0.000108335 0.108336
Potential -37426.3 386.944 386.939 -0.00633505 -6.33507
Kinetic En. 6690.03 208.658 208.657 -0.00205789 -2.0579
Total Energy -30736.3 542.66 542.655 -0.0083929 -8.39292
Temperature 298.008 9.29468 9.29464 -9.16688e-05 -0.091669
Pressure (bar) 2.36887 478.957 478.956 0.00256479 2.56479
Box-X 3.02334 0.01077 0.0107698 -2.24437e-07 -0.000224437
Volume 27.6361 0.295627 0.295621 -6.05586e-06 -0.00605588
Density (SI) 974.335 10.3936 10.3934 0.000223733 0.223733
Heat Capacity Cv: 12.49 J/mol K (factor = 0.00097278)
Isothermal Compressibility: 7.68593e-05 /bar
Adiabatic bulk modulus: 13010.8 bar
TIP3P with PME
LJ (SR) 5566.8 248.61 248.593 0.0111267 9.92947
Disper. corr. -155.928 1.80238 1.80221 -9.61068e-05 -0.0857659
Coulomb (SR) -606615 584.342 584.33 -0.0142947 -12.7567
Coulomb (LR) -199772 11.8148 11.8148 3.28827e-05 0.0293446
Potential -800976 419.16 419.159 -0.00323129 -2.88361
Kinetic En. 6690.07 224.102 224.099 -0.00426235 -3.80373
Total Energy -794286 595.936 595.933 -0.00749363 -6.68733
Temperature 298.009 9.98263 9.98251 -0.000189867 -0.169437
Pressure (bar) 2.35245 467.995 467.966 0.020043 17.8864
Box-X 3.01574 0.0116386 0.0116374 -6.4277e-07 -0.000573609
Volume 27.4285 0.317837 0.317804 -1.78581e-05 -0.0159366
Density (SI) 981.73 11.3478 11.3468 0.000605091 0.539984
Heat Capacity Cv: 12.4928 J/mol K (factor = 0.0011221)
Isothermal Compressibility: 8.95143e-05 /bar
Adiabatic bulk modulus: 11171.4 bar
Cheers,
Michael
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