Gibbs Project

Reproduction of published simulation data for H₂O

Contents

• SPC water
  
• SPCE water
  

SPC
Calculation of two points on the phase envelope of SPC water by GEMC-NVT runs and comparison with the results of de Pablo et al., J. Chem. Phys. 93, 7355-7359 (1990) and Mezei, Mol. Sim., 9, 257-267 (1992). All runs were started in the two phase region from two boxes with equal volume. The number of particles used in the simulation was N = 300. The results were obtained by averaging over the last 2*10⁶ steps (423 K) resp. 3.74*10⁶ steps (523 K).

• Results

• Temperature vs. density resp. Temperature vs. density logarithmic
• Temperature vs. potential energy
• Potential energy vs. density
• Numbers

Code	T(K)	rholiq. (g/cm3)	rhovap. (g/cm3)	Upot., liq. (kcal/mol)	Upot., vap. (kcal/mol)
de Pablo et al.	423	0.833(12)	0.00275(15)	-8.17(7)	-0.46(10)
Gibbs Project	423	0.834(4)	0.00266(41)	-8.09(4)	-0.45(31)
de Pablo et al.	523	0.658(25)	0.0476(60)	-6.64(15)	-2.09(22)
Gibbs Project	523	0.656(16)	0.0295(44)	-6.45(14)	-2.19(60)

• Performance of the runs:
• Run at T=423 K:
  The starting densities were rho_I = 0.7 g/cm³ and rho_II = 0.04 g/cm³ which corresponds to a starting feed density of rho_total = 0.3 g/cm³. Number of particles, densities, volumes and potential energies were equilibrated after 10⁶ steps.
  Progress of the run:
• Number of particles vs. configuration
• Density vs. configuration
• Volume vs. configuration
• Potential energy vs. configuration
  
• Report file
  
• Run at T=523 K:
  The starting densities were rho_I = 0.5 g/cm³ and rho_II = 0.06 g/cm³ which corresponds to a starting feed density of rho_total = 0.28 g/cm³. Number of particles, densities, volumes and potential energies were equilibrated after 1.5*10⁶ steps.
  Progress of the run:
• Number of particles vs. configuration
• Density vs. configuration
• Volume vs. configuration
• Potential energy vs. configuration
  
• Report file

• Final results
• Temperature vs. density logarithmic-linear
• Numbers

Code	T(K)	rholiq. (g/cm3)	rhovap. (g/cm3)
Alejandre et al.	328	0.981	0.0001
Gibbs Project	328	0.987(2)	0.00002(1)
Alejandre et al.	479	0.815	0.0052
Gibbs Project	479	0.811(9)	0.0044(7)

• Performance of the runs:
1. Run at T=328 K:
   The starting densities were rho_I = 0.84 g/cm³ and rho_II = 0.001 g/cm³ which corresponds to a starting feed density of rho_total = 0.05 g/cm³. Number of particles, densities, volumes and potential energies were equilibrated after 0.5* 10⁶ steps, note that there are only between 0 and 2 water molecules in the vapor phase after equilibration which causes poor statistics.
   Progress of the run:
• Number of particles vs. configuration
• Density vs. configuration
• Volume vs. configuration
• Potential energy vs. configuration

Report file

2. Run at T=479 K:
   This run was started farer off the equilibrium values with the densities rho_I = 0.6 g/cm³ and rho_II = 0.2 g/cm³ which corresponds to a starting feed density of rho_total = 0.4 g/cm³. Number of particles, densities, volumes and potential energies needed therefore 2.5*10⁶ steps to equilibrate.
   Progress of the run:
• Number of particles vs. configuration
• Density vs. configuration
• Volume vs. configuration
• Potential energy vs. configuration

Report file

Last modified by Johannes, July 31st 1996
Page created by Johannes, March 16th 1996