Size Effect on Transport Properties of Gaseous Argon: A Molecular Dynamics Simulation Study

Bulletin of the Korean Chemical Society.
2014.
May,
35(5):
1559-1561

- Received : December 15, 2013
- Accepted : January 19, 2014
- Published : May 20, 2014

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Results and Discussion

The mean square displacement (MSD) of gaseous argon increases nonlinearly over 500 ps and shows a straight line between 1000 and 3000 ps.,
1
but the MSD of liquid argon shows a linear behavior within 3 ps (see the inset of
Figure 2
in Ref. 1). The velocity auto-correlation (VAC) function also shows a dramatic difference. The VAC of liquid argon decays to 0 within 0.5 ps and has a negative value due to the collision with the neighboring particle (see the inset of
Fig.3
in Ref. 1), but the VAC of gaseous argon decays very slowly to 0 over 3000 ps.
1
Table 1
lists diffusion coefficients of the gaseous argon for N = 432, 1728, and 6912 at 273.15 at 1 atm obtained from MSD’s using Eq. (1) and VAC’s using Eq. (2) which are in good agreement with the experimental measures
4
and are superior to the predictions of the kinetic theory from mole-cular collision
4
as discussed in Ref.1. As the number of argon molecules increases, D obtained from MSD appro-aches the exact experimental measure (0.153→0.156→ 0.157) but D obtained from VAC lacks the accuracy (0.165 →0.154→0.156). The results using other LJ parameters
8
for N = 1728 are slightly better than those using the original LJ parameters.
Stress auto-correlation (SAC) and heat-flux auto-corre-lation (HFAC) functions of the gaseous argon at 273.15 K and 1 atm are plotted in
Figures 1
and
2
. Both correlation functions are monotonically decreased and decays very slowly to 0 over 3000 ps. In the inset of
Figure 1
, we plot the detailed SAC functions in the very narrow y-axis around the zero correlation. For N = 432, the fluctuation of the SAC function is very high, but it lowered with increasing number of argon molecules. The SAC function for N = 1728 is acceptable and that for N = 6912 is more perfect.
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Acknowledgements

This research was supported by Kyungsung University Research Grants in 2014. The com-putation for this work has been achieved by four PC clusters (Intel Xeon64 5620) for 2 months.

Lee S. H.
2013
Bull. Korean Chem. Soc
34
2931 -
** DOI : 10.5012/bkcs.2013.34.10.2931**

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** DOI : 10.5012/bkcs.2007.28.8.1371**

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Citing 'Size Effect on Transport Properties of Gaseous Argon: A Molecular Dynamics Simulation Study
'

@article{ JCGMCS_2014_v35n5_1559}
,title={Size Effect on Transport Properties of Gaseous Argon: A Molecular Dynamics Simulation Study}
,volume={5}
, url={http://dx.doi.org/10.5012/bkcs.2014.35.5.1559}, DOI={10.5012/bkcs.2014.35.5.1559}
, number= {5}
, journal={Bulletin of the Korean Chemical Society}
, publisher={Korean Chemical Society}
, author={Lee, Song Hi}
, year={2014}
, month={May}