Thermodynamic properties of some lanthanum and lanthanide halides: II. Thermodynamic functions of gaseous molecules LnX (Ln = Ce−Lu, X = F, Cl)

Abstract

The molecular constants of LnF (Ln = Ce−Lu) for the ground state have been estimated based on the available spectroscopic characteristics of lanthanum and lanthanide monofluorides. These constants have been used for calculating the reduced Gibbs energy (−[G 0(T) − H 0(0)]/T) of the compounds in the ideal gas state in the range 298.15–3000 K at the standard pressure p 0 = 0.1 MPa. The rigid rotator-harmonic oscillator approximation with additional inclusion of the anharmonicity of oscillations (by the method of Mayer and Goeppert-Mayer) and correction for centrifugal stretching have been used. The contribution made by electronic excitation has been calculated by two methods: based on the energies of the excited states of molecules and based on the electronic excitation energy of the free Ln+ ion. Analogous data are reported for lanthanide monochlorides.