Quantum effects in the solid-liquid phase diagram of Ne13 and (para-H2)13

Applying the Fourier path-integral formalism to the isothermal-isobaric ensemble, the melting transition for Ne-13 and (para-H-2)(13) was characterized at various pressures. All multidimensional integrals were solved using the parallel tempering Monte Carlo algorithm. The volume of the system was defined with respect to the centroids of the quantum particles, and the maximum value of the constant pressure heat capacity at a given temperature was used to identify the melting temperature. Pressure versus temperature phase diagrams were constructed for these systems with and without the inclusion of quantum effects. It was observed that for neon the quantum contribution slightly decreases the melting temperature in the phase diagram, in particular at high pressure. For (para-H-2)(13), quantum effects considerably reduce the melting temperature at all pressures and pressure effects are more pronounced than in Ne-13. (C) 2002 American Institute of Physics.