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Topics - SierraEcho

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Dear raspa community,

currently, I am working on simulations within cylindrical pores. Due to the fact that I have a cylinder inside a cartesian cell, the corners, filled with framework atoms, contribute quite a lot
to the overall volume of the unit cell.

I assume that this non-void volume highly increases the necessary calculation time because an adsorptiv molecule could be placed there which results in the calculation of the LJ-potential for all atoms within the surrounding area. Obviously, this move will be rejected due to the high potential energy.
Here comes the idea: would it be possible to reduce the calculation effort by using a block-pocket file (exemplary marked as red circles). The necessary key information actually is if the block-pocket criteria is checked before the LJ-potential is calculated for a given MC-move.

Many thanks for your help!

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General / High-Pressure Simulations
« on: July 12, 2021, 03:01:33 PM »
Dear RASPA-Community,

currently I am thinking to use RASPA in order to simulate some High-Pressure isotherms. Before starting with any kind of simulation in pores,
I thought it's a good idea to simulate both a rho-P (GCMC, supercritical) and a rho_T diagramm (Gibbs-Ensemble, subcritical).

To sum the results up: the subcritical results are good (as expected), but the high pressure results tend to have quite pronounced deviations (about 9% at 90 bar).

I was woundering about possible reasons for that, however I couldn't really come to a clear result. So my idea is that a: the mistake comes from the
use of the Peng-Robinson-EOS which is implemented as default EOS as far as I know b: at elevated pressure, it's not a valid assumption to neglect three-body
interactions anymore and/or the forcefield is not optimized for such high pressures. Is there anybody who conducted HP simulations and has an idea if
there is a possible solution or if a mistake of 9% is in spec at those elevated pressures?

Attached, you find my input file and a results plot.

Thanks for your input/help/ideas in advance :)

SimulationType                MonteCarlo
NumberOfCycles 50000
NumberOfInitializationCycles 50000
PrintEvery                    100

ContinueAfterCrash            no

ChargeMethod                  Ewald
Forcefield                    TraPPE
RemoveAtomNumberCodeFromLabel yes
Cutoff 12.8
EwaldPrecision                1e-6

Box 0
BoxLengths 30 30 30
ExternalTemperature 298
ExternalPressure 9e6

Movies no
WriteMoviesEvery 10000

Component 0 MoleculeName             methane
            StartingBead             0
            MolFraction              1
            MoleculeDefinition       TraPPE
            IdealGasRosenbluthWeight 1
            TranslationProbability   1
            RotationProbability      1
            ReinsertionProbability   1
            SwapProbability          1
            CreateNumberOfMolecules  0
            WidomProbability         0





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