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[lammps-users] pressure fluctuation
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[lammps-users] pressure fluctuation

From: Hossein Geraili <geraili.hsn@...24...>
Date: Sun, 3 Sep 2017 21:11:52 +0430

Dear Lammps users,

I simulated a box of 200 of ionic liquid molecules in NVT ensemble using:

pair_style   lj/cut/coul/long  11

kspace_style pppm 1.0e-4
fix         2 all ave/time 100 1000 100000 c_thermo_press file pressure.txt

The pressure results are not well-fitted with experimental data. I chose 1 ns for run time, and the error percent between two following average pressures is about 10%. I wanted to know is it possible, if I increase the simulation time like to 10 ns, the error percent would decrease below 2 or 3 percent? My main problem is the pressure fluctuation because when I compare the pressure results with experimental it produces a great error, but the corresponding volume is ok!!!!! I mean, I have pVT data from the simulation, and when I compare them with pVT data of experiments, for same VT between exp. and sim. I have really different pressures( like 500% error percent in average); but when I compare the corresponding V for same pT of sim. and exp. the error percent is below 3%. I don't understand, is my simulation could be validated via experimental result or not?

error percent=((P2-P1)/P1)*100
Hosein Geraili Daronkola
M.Sc.Graduated of physical chemistry
Physical Chemistry,
Department of Chemistry,
Sharif University of Technology.