NEWS

A recent work published in Physical Review B

Last update: October 22, 2010

"Thermodynamic stability of hydrogen hydrades of ice Ic and II structures"

  • Lukman Hakim, Kenichiro Koga, and Hideki Tanaka

 

--------------------------------------------------

* Abstract *

--------------------------------------------------

The occupancy of hydrogen inside the voids of ice Ic and ice II, which gives two stable hydrogen hydrate compounds at high pressure and temperature, has been examined using a hybrid grand-canonical Monte Carlo simulation in wide ranges of pressure and temperature. The simulation reproduces the maximum hydrogen-to-water molar ratio and gives a detailed description on the hydrogen influence toward the stability of ice structures. A simple theoretical model, which reproduces the simulation results, provides a global phase diagram of two-component system in which the phase transitions between various phases can be predicted as a function of pressure, temperature, and chemical composition. A relevant thermodynamic potential and statistical-mechanical ensemble to describe the filled-ice compounds are discussed, from which one can derive two important properties of hydrogen hydrate compounds: the isothermal compressibility and the quantification of thermodynamic stability in term of the chemical potential.

© 2010 The American Physical Society