A NEW EQUATION OF STATE FOR SOLID para-HYDROGEN

Wang, Lecheng

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https://hdl.handle.net/2142/79457 Copy

Description

Title

A NEW EQUATION OF STATE FOR SOLID para-HYDROGEN

Author(s)

Wang, Lecheng

Contributor(s)

• Roy, Pierre-Nicholas
• Le Roy, Robert J.

Issue Date

25-Jun-15

Keyword(s)

Cold/Ultracold/Matrices/Droplets

Abstract

Solid textit{para}-H$_2$ is a popular accommodating host for impurity spectroscopy due to its unique softness and the spherical symmetry of textit{para}-H$_2$ in its textit{J}=0 rotational level.footnote{,T. Momose, H. Honshina, M. Fushitani and H. Katsuki, {em Vib. Spectrosc.} {bf 34}, 95(2004).}$^,$footnote{,M. E. Fajardo, {em J. Phys. Chem. A} {bf 117}, 13504 (2013).} To simulate the properties of impurity-doped solid textit{para}-H$_2$, a reliable model for the `soft' pure solid textit{para}-H$_2$ at different pressures is highly desirable. While a couple of experimentalfootnote{,I. F. Silvera, {em Rev. Mod. Phys.} {bf 52}, 393(1980).} and theoreticalfootnote{,F. Operetto and F. Pederiva, {em Rhys. Rev. B} {bf 73}, 184124(2006).} studies aimed at elucidating the equation of state (EOS) of solid textit{para}-H$_2$ have been reported, the calculated EOS was shown to be heavily dependent on the potential energy surface (PES) between two textit{para}-H$_2$ that was used in the simulations.footnote{,T. Omiyinka and M. Boninsegni, {em Rhys. Rev. B} {bf 88}, 024112(2013).} The current study also demonstrates that different choices of the parameters governing the Quantum Monte Carlo simulation could produce different EOS curves. To obtain a reliable model for pure solid textit{para}-H$_2$, we used a new 1-D textit{para}-H$_2$ PES reported by Faruk {it et al.}footnote{,N. Faruk, M. Schmidt, H. Li, R. J. Le Roy, and P.-N. Roy,{em J. Chem. Phys.} {bf 141}, 014310(2014).} that was obtained by averaging over Hinde's highly accurate 6-D H$_2$--H$_2$ PES.footnote{,R. J. Hinde, {em J. Chem. Phys.} {bf 128}, 154308(2008).} The EOS of pure solid textit{para}-H$_2$ was calculated using the PIMC algorithm with periodic boundary conditions (PBC). To precisely determine the equilibrium density of solid textit{para}-H$_2$, both the value of the PIMC time step (tau) and the number of particles in the PBC cell were extrapolated to convergence. The resulting EOS agreed well with experimental observations, and the {it hcp} structured solid textit{para}-H$_2$ was found to be more stable than the {it fcc} one at 4.2K, in agreement with experiment. The vibrational frequency shift of textit{para}-H$_2$ as a function of the density of the pure solid was also calculated, and the value of the shift at the equilibrium density is found to agree well with experiment.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

Permalink

http://hdl.handle.net/2142/79457

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