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Hi,

I am studying the adsorption of small molecules (carbon dioxide, propane, methane) in zeolite 13X using GCMC in RASPA. I am using the forcefield of Calero et al. (2004) and Garcia-Sanchez et al. (2009) for the same. Is there a general rule of thumb for the acceptance rate (For ex. >= 50%) of swap moves (insertion and deletion) in GCMC simulations for adsorption in porous materials?
Can this rate be increased by increasing the number of initialization (plus equilibration) cycles in GCMC simulations ?

Regards,
Rajasi

Hello,

I am studying the adsorption of carbon dioxide in zeolite 13X. I have the .cif file of framework and the coordinates of carbon dioxide and sodium ions in the .pdb file for every frame that is generated. How do I visualize every frame of the movie file, along with the framework .cif file in iRASPA ? I want to visually inspect adsorption sites in 13X zeolite.

Thanks,
Rajasi

Hello Dr. Dubbeldam,

I have been running adsorption simulations in RASPA 2.0 using the High Performance Computing Center (HPCC) of my University. I recently installed RASPA 2.0.45 on HPCC and some of my current simulations crashed due to wall time limit on the cluster. I always use ContinueAfterCrash option in the simulation.input file, so that the simulation continues after the point it was crashed. However, it looks like RASPA 2.0.45 does not recognize crash file of RASPA 2.0 and the simulation starts again from the beginning. Is this to expected when running files from an older version on the latest version ?

Regards,
Rajasi

Hello,

I have a question regarding RandomAlSubstitution to modify the Si/Al ratio in zeolite 13X. In the manual, it is written that the 'Substitute' command is useful to have the same structure, whereas the 'RandomlySubstitute' command may not keep the same space group. I want to substitute 10 Al atoms by 10 Si atoms in the framework. How many 'Substitute' commands do I need to consider in the input file, so as to keep the space group in the fd-3, with 96 elements ? How do I check if the same space group is followed at the end of simulation.

Regards,
Rajasi

Hello,

I have modified the base file of NaX, available in RASPA to suit the Si/Al ratio, which I want. The base file in RASPA has Si/Al = 1 (96 Si, 96 Al). For my simulations, I need Si/Al = 1.23 (106 Si, 86 Al), differentiating the oxygen atoms based on connectivity to Si or Al. I have changed the base file using RASPA simulations, whose input file is given below.  RASPA generates an output file in the Movie folder, titled 'Framework_0_final_1_1_1.cif',  which I have attached in this post. This file has 86 Al and 106 Si, meaning that random substitution has worked. My question is as follows :

Why is iRASPA unable to visualize this file? There are total 576 atoms/ unit cell. When I upload the modified file, it only reads 232 atoms and the structure generated is not right. However, VESTA is able to generate the correct structure. I would really appreciate it if you could help me with this.

Thanks,
Rajasi

INPUT :

SimulationType                MC
NumberOfCycles                0
NumberOfInitializationCycles  0
PrintEvery                    10
     
Forcefield                      local
UseChargesFromCIFFile           yes

RandomlySubstitute 10 Al1 Si1

ModifyFrameworkAtomConnectedTo O1 Oa1 Al1
ModifyFrameworkAtomConnectedTo O2 Oa2 Al1
ModifyFrameworkAtomConnectedTo O3 Oa3 Al1
ModifyFrameworkAtomConnectedTo O4 Oa4 Al1
     
Framework 0
FrameworkName NaX
UnitCells 1 1 1
ExternalTemperature 293

Does RASPA have the capability to do simulated Annealing? If so, how to specify the temperature range for annealing?

Dear all,

The pseudo_atom radii for N_N2 and NCOM_N2  are 0.7 in the pseudo_atoms.def file. The model for N2 molecule is taken from Potoff and Siepmann as the charge values for N and NCOM match with the partial charges given to these sites of N2 molecule of Potoff and Siepmann. How is the pseudo atom radius of 0.7 defined? What is the basis for the same. The experimental bond length of N2 molecule is 1.1 A.
The reason I am asking this question is because I want to define the pseudo_atoms for two CO models developed by Calero et al  (2012) and Piper et al (1984). For these models, I have the LJ parameters, charges and the distance of the sites from the COM of the molecule. What should be the basis to define the pseudo_atom radii for each site of these models?

Thanks,
Rajasi