Bulk Density Validation by MC

[Bourne]

Dear Dr. Dubbeldam and RASPA users,

I am a beginner with the RASPA software and am conducting a study on gas occurrence behaviors within porous rock. As part of my study, I am performing validation work on the fluid model by calculating the bulk density within an empty box at 333K using MC simulations. I have tested the TraPPE and EPM2 models. However, the results are unsatisfactory, as both bulk density values deviate from the data provided by NIST and the P-R equation, despite the systems being well equilibrated. This discrepancy is confusing, and I've tried various approaches without success. I have checked all the input files, and they appear to be correct. Could you please advise on how I might resolve this issue?

Thank you for your time.

Best regards,

Input files for TraPPE Model Validation:

SimulationType                          MonteCarlo
NumberOfCycles                          20000
NumberOfInitializationCycles            6000
PrintEvery                              1000
RestartFile                            no

ChargeMethod                            Ewald
EwaldPrecision                          1e-5
Forcefield                              TraPPE
RemoveAtomNumberCodeFromLabel          no 

Box                                    0
BoxLengths                              25 25 25

ExternalTemperature                    333.0
ExternalPressure                        5e6 10e6 15e6 20e6 25e6 30e6

Movies                                  yes
WriteMoviesEvery                        2000
           
Component 0 MoleculeName                CO2
            MoleculeDefinition          TraPPE
            TranslationProbability      0.5
            RotationProbability        0.5
            ReinsertionProbability      0.5
            SwapProbability            1.0
            CreateNumberOfMolecules    0