Recent Posts

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General / Phase state in MC simulation of grand canonical ensemble
« Last post by alexam on August 09, 2022, 08:17:47 PM »
Dear all,

checking the output of a Monte Carlo simulation in the grand canonical ensemble, I found "Vapour=stable, Liquid=metastable" stated for each component of a mixture (beginning of the output). This simulation considers water and alcohols in a silica zeolite.

In the manual I could find examples for the same line as "Fluid is a vapour", so I understand it's reporting the phase state of the compound, but I could not find additional explanation to those stable/metastable states.

The only similar citation I could find in the literature (https://pubs.acs.org/doi/10.1021/acsami.8b09343) says that:
"In the case of a hysteresis, for one relative pressure, two states are found. One of the states is a metastable state, and the another is a stable state."

Questions:
a) So, what exactly does RASPA output means with the "Vapour=stable, Liquid=metastable"?
b) Is it somehow related with hysteresis, as mentioned by the article above?

Thanks in advance.
Best regards
2
Visualization / RASPA visualization (Density Plot)
« Last post by yimin88 on July 30, 2022, 03:44:59 PM »
Hi Prof. Dubbeldam

I hope you are doing well.

when I am trying to run example of density plot in the file (RASPA/examples/Visualization/UnitCell/Density/ERI) from your official github code, I found that the simulated results is not the same as your results written from your official document in Page 171.

Could you help to solve my problem?

I am looking forward to your reply.


3
Input files and parameters / Re: Idealgasrosenbluchweight
« Last post by peter on July 16, 2022, 01:00:43 PM »
Thank you for answer. I followed the published example. The EOS for n hexane is reproduced from TRAPPE. Regards Piotr
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Input files and parameters / Re: Idealgasrosenbluchweight
« Last post by David Dubbeldam on July 14, 2022, 07:43:34 PM »
The ideal gas Rosenbluth weight is only depending on temperature. For each temperature you can pre-compute it (see examples).
5
Many thanks, got it working now!
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Input files and parameters / Idealgasrosenbluchweight
« Last post by peter on July 05, 2022, 04:10:13 PM »
Hi, I hope you are all doing well. Just short question.
At particular temperature, we need to compute idealgasrosenbluvhweight for cbmc. Is this parameter
The same for bulk and confined fluid ? If not it must be recalculated for all porous materials ? Cheers piotr

7
Thank you, Dr. Dubbeldam. It's nice that we can set up both VDW and Coulomb cutoffs individually in RASPA!
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The 'CutOffVDW' should not be different for the gas and liquid phase, otherwise you're using different force fields for them.
The 'CutOffCoulomb' should be set to something slightly smaller than half the box size. This significantly speeds up the computation for the gas-phase since the gas-phase box can be large.
Importantly, both can be set per system (just list them after the 'Box' statement).
9
Hi,

I just started learning RASPA and I am trying to set up a Gibbs Ensemble VLE, the previous software I used (MCCCS-MN) allowed me to have a different cut-off length for vapor and liquid boxes. I was trying to use 2 different ones where the box is defined in the simulation input file for Raspa.. but it seems like it only reads it from the Force Field definition sections and can take only a single value for both the boxes. Is there a way to work around that?
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General / Henrys Constant output
« Last post by bphan on June 23, 2022, 07:46:06 PM »
Hi,
Im having trouble with the output for Henrys Constant. The units are mol/kg*Pa, and for each molecule im calculating it for there are conversions (see attached). When im converting it, to account for the gas, do I have to also multiple by other things? ie the mg/g conversion?
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