Hi everyone,
I have problem in using lammps for investigating water adsorption on MOFs. I want to determine water uptake in mof adsorbent. But I dont know how to determine the number of water molecules corresponding to a relative pressure. In this process the total pressure is atmospheric and a part of this pressure is related to water partial pressure. How can I determine the number of water molecules corresponding to a relative pressure value?
Hello,
To equilibrate the content in fluid in a porous material, there are two methods that I am aware of:
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- placing the porous material directly into contact with a very large reservoir, and wait for the system to equilibrate. This may work for some particular fluid pressure and density values, but in general this is not feasible as it would require simulating a huge reservoir,
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- using the GCMC method (it can be done in LAMMPS using fix GCMC), where the chemical potential (or pressure) of a fictitious reservoir is imposed. The GCMC method consists in trying to add and delete molecules in the porous material until the chemical potential of the fluid within the material is the same as the chemical potential of the reservoir. It is usually less computationally expansive than simulating explicitly the reservoir, although it can still be quite slow (and not easily to parallelize).
Simon
Thanks for the reply,
The most related papers have used gcmc. But they said that for each partial pressure, a specified number of water molecules iserted in the simulation, while the total pressure is atmospheric.