Radial Distribution Function Study of Noble Dense Fluid Argon at Varying Degrees of Disorder Using LAMMPS

Authors : Aporva Koubey and Poonam Tandon*

This abstract is a beginners attempt to understand the dynamics of a noble dense fluid argon as we go from the strongly correlated (solid) state to the weakly correlated (liquid) state to less dense (gaseous) state using the LAMMPS software. We use LAMMPS software to understand the collective dynamics of the solid Argon state that is strongly correlated exhibiting quantised collective vibrational modes. The radial distribution function exhibits distinct peaks at the well-defined atomic positions. As we move on to the liquid state we observe that the system becomes weakly correlated thus losing its translational invariance. In a liquid both the collective and single particle dynamics play a significant role. The behaviour of a liquid is being studied by the radial distribution function. the temperature variance helps us to go from a strongly correlated liquid argon (as in Rahman molecular dynamic paper for T=120K, Density=1.374g/cc)to the weakly correlated argon (in Bafile experimental paper for T=301.5K, P=20MPa, Density=0.334g/cc)  to still less correlated (T=301.5K, P=8MPa,Density=0.133g/cc). The radial distribution values calculated using the LAMMPS software can give us an insight into the intriguing behaviour of fluids thus explaining how the collective and single particle dynamics is exhibiting itself. There is considerable insight which can be understood with accurate molecular dynamic simulation(using LAMMPS) thus helping the theoretical physicists. The LAMMPS software helps us to understand through the radial distribution function the least correlated gaseous state of argon.