Case study

Results

Molecular Dynamics (MD) simulations were performed to compute the mean-squared displacement (\(MSD\)), self-diffusivity constant (\(D\)), dynamic viscosity (\(\eta\)), isochoric heat capacity (\(Cv\)), and the thermal conductivity (\(k\)) of liquid Argon. To do this, we performed a sensitivity analysis by varying the number of Ar atoms (N) in the system (N = 128, 256, 512, 1024, and 2048), force field parameters obtained from three sources (Barker-Fisher-Watts, Rahman, and White), integration steps (dt = 0.5, 1, and 2 femtoseconds), and the method used to evaluate the atomic forces (a simple method that scales with \(~N^2\) and a Verlet lists method that scales with \(~N\). The sensitivity study consists of 90 simulations in total. The following page presents the results obtained in two large tables (Table 1 containing the results using the simple force evaluation method, and Table 2 containing the results obtained from using the Verlet lists method). The trajectories' files produced by Scymol are available for download in the Comments column of the tables.

Table 1. Sensitivity analysis results obtained using the simpler, and slower method to evaluate forces of Type 2 in the system. The number of force evaluations increases with \(~N^2\).

Parameters	N	Time-step (\(ps\))	Temperature (\(K\))	MSD (\(Å^2\))	Diffusivity (\(Å^2/ps\))	Viscosity	Heat capacity (\(E/K/{atom}\))	Thermal conductivity	Comments
Barker-Fischer-Watts	128	0.5	xx	xx	xx	xx	xx	xx	cc
		1	xx	xx	xx	xx	xx	xx	cc
		2	xx	xx	xx	xx	xx	xx	cc
	256	0.5	xx	xx	xx	xx	xx	xx	cc
		1	xx	xx	xx	xx	xx	xx	cc
		2	xx	xx	xx	xx	xx	xx	cc
	512	0.5	xx	xx	xx	xx	xx	xx	cc
		1	xx	xx	xx	xx	xx	xx	cc
		2	xx	xx	xx	xx	xx	xx	cc
	1024	0.5	xx	xx	xx	xx	xx	xx	cc
		1	xx	xx	xx	xx	xx	xx	cc
		2	xx	xx	xx	xx	xx	xx	cc
	2048	0.5	xx	xx	xx	xx	xx	xx	cc
		1	xx	xx	xx	xx	xx	xx	cc
		2	xx	xx	xx	xx	xx	xx	cc
Rahman	128	0.5	xx	xx	xx	xx	xx	xx	cc
		1	xx	xx	xx	xx	xx	xx	cc
		2	xx	xx	xx	xx	xx	xx	cc
	256	0.5	xx	xx	xx	xx	xx	xx	cc
		1	xx	xx	xx	xx	xx	xx	cc
		2	xx	xx	xx	xx	xx	xx	cc
	512	0.5	xx	xx	xx	xx	xx	xx	cc
		1	xx	xx	xx	xx	xx	xx	cc
		2	xx	xx	xx	xx	xx	xx	cc
	1024	0.5	xx	xx	xx	xx	xx	xx	cc
		1	xx	xx	xx	xx	xx	xx	cc
		2	xx	xx	xx	xx	xx	xx	cc
	2048	0.5	xx	xx	xx	xx	xx	xx	cc
		1	xx	xx	xx	xx	xx	xx	cc
		2	xx	xx	xx	xx	xx	xx	cc
White	128	0.5	xx	xx	xx	xx	xx	xx	cc
		1	xx	xx	xx	xx	xx	xx	cc
		2	xx	xx	xx	xx	xx	xx	cc
	256	0.5	xx	xx	xx	xx	xx	xx	cc
		1	xx	xx	xx	xx	xx	xx	cc
		2	xx	xx	xx	xx	xx	xx	cc
	512	0.5	xx	xx	xx	xx	xx	xx	cc
		1	xx	xx	xx	xx	xx	xx	cc
		2	xx	xx	xx	xx	xx	xx	cc
	1024	0.5	xx	xx	xx	xx	xx	xx	cc
		1	xx	xx	xx	xx	xx	xx	cc
		2	xx	xx	xx	xx	xx	xx	cc
	2048	0.5	xx	xx	xx	xx	xx	xx	cc
		1	xx	xx	xx	xx	xx	xx	cc
		2	xx	xx	xx	xx	xx	xx	cc

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