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Ground- And Excited-State Properties Of Solid Argon Under Pressure, Richard Alan Lesar
Ground- And Excited-State Properties Of Solid Argon Under Pressure, Richard Alan Lesar
Richard Alan Lesar
A self-consistent perturbation model for calculating the ground- and excited-state electronic properties of molecular and rare-gas crystals is presented. A tight-binding approximation is used, in which the effects of the crystal potential, calculated with local-density functionals, are included as a perturbation on the molecules (or atoms). The molecular (atomic) wave functions are then computed from standard Hartree-Fock theory. For the case of solid argon under pressure, a decrease in atomic volume causes a gain in free energy, which is partially balanced by the energy required to compress the atom. Calculated exciton energies for Ar disagree by only 2.5% with experimental …
Polarizability And Quadrupole Moment Of A Hydrogen Molecule In A Spheroidal Box, Richard Alan Lesar, D. R. Herschbach
Polarizability And Quadrupole Moment Of A Hydrogen Molecule In A Spheroidal Box, Richard Alan Lesar, D. R. Herschbach
Richard Alan Lesar
The polarizability and quadrupole moment of a hydrogen molecule enclosed within an infinite-walled spheroidal box are calculated as functions of the hox size, for a range corresponding to nominal pressures up to lo5 kbar. A five-term James and Coolidge variational wave function is employed and the Kirkwood approximation is used for the polarizability. Comparison is made with similar calculations for the H2+ molecule-ion and the II atom, and also with recent density-functional calculations. The box model proves to greatly exaggerate the compression of the H2 bond with pressure but nonetheless yields a realistic correlation of vibrational frequency with internuclear distance. …
Density‐Functional Theory For Solid Nitrogen And Carbon Dioxide At High Pressure, Richard Alan Lesar, R. G. Gordon
Density‐Functional Theory For Solid Nitrogen And Carbon Dioxide At High Pressure, Richard Alan Lesar, R. G. Gordon
Richard Alan Lesar
Structural properties of solid N2 and CO2 under pressure have been studied with a recently reported theory. The model allows for calculation of the structure and dissociation energy of molecular crystals, using no empirical parameters where dispersion energy is included as a sum of the pair interactions. Comparison with available low temperature experimental results shows good agreement with average errors in lattice constants of about 1% and in lattice energies of about 6%. Calculations were performed on nitrogen in a number of structures, including the experimentally observed P a3 (α), P42/m n m (γ), P63/m m c (β), and P …
Equation Of State Of Fluid Nh3 From P-V-T And Ultrasound Measurements To 12 Kbar, R. L. Mills, D. H. Lienbenberg, Richard Alan Lesar, Ph. Pruzan
Equation Of State Of Fluid Nh3 From P-V-T And Ultrasound Measurements To 12 Kbar, R. L. Mills, D. H. Lienbenberg, Richard Alan Lesar, Ph. Pruzan
Richard Alan Lesar
A piston-cylinder apparatus was used to measure the pressure, volume, temperature, and ultrasonic velocity (P,V,T,u) of fluid NH3 from 195 to 320 K at pressures up to 12 kbar. Over 1200 sets of P-V-T-u and P-V-T data were fitted to a Tait-type equation of state (EOS) by non-linear least-squares minimization. With quadratic terms in T for the two fitted parameters, the rms deviation is ± 0.2% in V and ± 0.9% in u, which is comparable to the experimental error. The simple Tait EOS is useful over the entire fluid range between the vaporization and melting curves up to T …