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[lammps-users] Lennard-Jones 2D pressure changes with potential cut off

# [lammps-users] Lennard-Jones 2D pressure changes with potential cut off

 From: sindhana@...7053... Date: Thu, 10 Aug 2017 16:27:39 +0530

```Dear All,

Version of LAMMPS: 5 May 2012

I ran a 2D simulation of Lennard-Jones particles at various temperatures
and densities using an NVT ensemble and noted that the pressure (after
including long-range correction) increases with increasing cut off length
used for the potential.

pair potential used: lj/charmm/coul/charmm
Charge on particles: 0

The system contains 2500 particles and was run with periodic boundary
conditions. All data stated below are in Lennard-Jones units. I used the
expression given below for long-range correction.

P_correction=12/5(pi)*(rho)^2*[(1/r_i)^10-5/4*(1/r_i)^4]

rho=density, T=temperature, P=pressure, delta P=uncertainty in pressure,
pi=3.14, r_i=inner cut-off radius used for potential, r_o=outer cut-off

T	rho	r_i	r_o	P	delta P
0.5	0.75	3.0	3.1	0.2936	0.0014
3.5	3.6	0.3065	0.0016
4.0	4.1	0.3216	0.0007
4.5	4.6	0.3230	0.0024

0.7	0.75	3.0	3.1	1.1724	0.0026
3.5	3.6	1.1874	0.0028
4.0	4.1	1.2020	0.0031
4.5	4.6	1.2037	0.0023

1.0	0.75	3.0	3.1	2.3817	0.0037
3.5	3.6	2.3951	0.0019
4.0	4.1	2.4063	0.0037
4.5	4.6	2.4116	0.0030

1.0	0.50	3.0	3.1	0.5510	0.0010
3.5	3.6	0.5589	0.0008
4.0	4.1	0.5648	0.0008
4.5	4.6	0.5658	0.0004

1.4	0.10	3.0	3.1	0.1386	0.0001
3.5	3.6	0.1390	0.0001
4.0	4.1	0.1391	0.0001
4.5	4.6	0.1392	0.0001

Regards,
Sindhana Selvi P.S.
Masters student (Physics)
Indian Institute of Science

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