Dear Dubbeldam,
I'm using RASPA to simulate the alkane adsorption in Montmorillonite. But in the output , the absolute adsorption is zero, the excess loading is negative, I don't know why and how to get the correct amount of adsorption.
Kind regards,
Yadi Jiang
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This is the component's critical parameter:792K, 0.98MPa, 0.8.
(In the simulation, temperature is 358K, pressure is 30MPa,40MPa.)
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This is the simulation.input file:
SimulationType MonteCarlo
NumberOfCycles 100000
NumberOfInitializationCycles 50000
PrintEvery 1000
RestartFile no
ContinueAfterCrash no
WriteBinaryRestartFileEvery 5000
ChargeMethod Ewald
Forcefield clayff //Custom force field
CutOffVDW 12.5
RemoveAtomNumberCodeFromLabel no
Framework 0
FrameworkName 10-MMT
UseChargesFromCIFFile no
UnitCells 3 3 3
HeliumVoidFraction 1
ExternalTemperature 358
ExternalPressure 3e7 4e7
Movies yes
WriteMoviesEvery 5000
ComputeDensityProfile3DVTKGrid yes
WriteDensityProfile3DVTKGridEvery 1000
DensityProfile3DVTKGridPoints 150 150 150
AverageDensityOverUniteCellsVTK yes
DensityAverageTypeVTK FullBox
Component 0 MoleculeName C22
MoleculeDefinition TraPPE
TranslationProbability 1.0
RotationProbability 1.0
ReinsertionProbability 1.0
IdentityChangeProbability 0.0
SwapProbability 1.0
CreateNumberOfMolecules 0
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The force field parameter:
# general rule for shifted vs truncated
shifted
# general rule tailcorrections
no
# number of defined interactions
4
# type interaction, parameters. IMPORTANT: define shortest matches first, so that more specific ones overwrites these
O_ lennard-jones 78.263 3.5532
Al_ lennard-Jones 0.00067 4.7943
Si_ lennard-Jones 0.000926 3.7064
Ca_ lennard-Jones 50.362 3.2237
# general mixing rule for Lennard-Jones
Lorentz-Berthelot
Negative excess adsorption indicates that you are in the liquid phase. That happens when you go above the vapor pressure.
Dear Dr. Dubbeldum
I am using RASPA to calculate propane/propene selectivity of pure silica zeolite LTA using the following code. In output absolute loading for both propane and propene is positive, But excess loading is negative. Then I tried this simulation in 1 bar pressure, But excess loading is negative. Thanks a lot for guiding me.
SimulationType MonteCarlo
NumberOfCycles 100000
NumberOfInitializationCycles 10000
PrintEvery 1000
RestartFile no
ContinueAfterCrash no
WriteBinaryRestartFileEvery 500
Forcefield local
UseChargesFromCIFFile yes
Framework 0
FrameworkName Framework_0_final_1_1_1
UnitCells 3 3 3
HeliumVoidFraction 0.460673
ExternalTemperature 308.37
ExternalPressure 1970000
Movies yes
WriteMoviesEvery 1000
Component 0 MoleculeName propene
MoleculeDefinition local
IdealGasRosenbluthWeight 1.0
MoleFraction 0.91
TranslationProbability 0.5
RotationProbability 0.5
ReinsertionProbability 0.5
IdentityChangeProbability 1.0
NumberOfIdentityChanges 2
IdentityChangesList 0 1
SwapProbability 1.0
CreateNumberOfMolecules 0
Component 1 MoleculeName propane
MoleculeDefinition local
IdealGasRosenbluthWeight 1.0
MoleFraction 0.09
TranslationProbability 0.5
RotationProbability 0.5
ReinsertionProbability 0.5
IdentityChangeProbability 1.0
NumberOfIdentityChanges 2
IdentityChangesList 0 1
SwapProbability 1.0
CreateNumberOfMolecules 0