A NEW POTENTIAL ENERGY SURFACE FOR H$_2$--N$_2$O AND PIMC SIMULATION PROBING SUPERFLUIDITY AND VIBRATIONAL FREQUENCY SHIFTS IN DOPED $para$-H$_2$ CLUSTERS

Author Institution: Guelph-Waterloo Centre for Graduate Work in Chemistry and; Biochemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada; School of Chemistry and Chemical Engineering, Nanjing University; Nanjing, Jiangsu, ChinaThe existence of superfluidity of $para$-hydrogen clusters doped by the linear molecules\ {\bf 105}, 133401 (2010).}$^,$\ {\bf 132}, 064501 (2010).}$^,$\ {\bf 108}, 253402 (2012).}~ such as CO, CO$_2$ and OCS stimulated our theoretical study of ($para$-H$_2$)$_N$--N$_2$O clusters. A new 6D $ab \ initio$ PES for the H$_2$--N$_2$O dimer which explicitly included the symmetric and asymmetric vibrational coordinates $Q$$_1$ and $Q$$_3$ of N$_2$O was constructed. Four-dimensional global intermolecular PESs were then obtained by fitting the vibrational averaged interactions energies for $\nu_3$(N$_2$O)=0 and 1 to the Morse/Long Range(MLR) analytical form with theoretically fixed long-range parameters. Using the adiabatic hindered-rotor approximation, effective two-dimensional PESs for the $para$-H$_2$--N$_2$O dimer were then generated. Predictions of the infrared spectra of $para$-H$_2$--N$_2$O based on these PESs have been in good agreement with the experimental observations.\ {\bf 117}, 8308 (2002).}~ Based on these surfaces, predictions of structural properties, vibrational band origin shifts, rotational dynamics and superfluidity of ($para$-H$_2$)$_N$--N$_2$O clusters have been generated using bosonic PIMC simulation methods. The evolution of the calculated shifts agreed reasonably with that for the experimental observations.\ {\bf 123}, 114314 (2005).}~ Reduction of the effective moment of inertia is predicted to occur when the dopant is partially surrounded by the $para$-H$_2$ solvent, which marked the onset of molecular superfluidity in $para$-H$_2$. Results obtained using our surfaces and PIMC algorithm will be presented