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A Quasi‐Harmonic Calculation of Lattice Dynamics for Na
Author(s) -
Ho P. S.,
Ruoff A. L.
Publication year - 1967
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.19670230208
Subject(s) - pseudopotential , condensed matter physics , phonon , neutron scattering , anharmonicity , ion , electron , lattice (music) , dispersion relation , chemistry , scattering , thermodynamics , physics , quantum mechanics , acoustics
We have applied a phenomenological model for a quasi‐harmonic calculation of the lattice dynamics for Na. The lattice potential is separated into the electrostatic energy, the ion‐core exchange repulsion and the screened electron‐ion potential. The ion exchange term is taken to be the Born‐Meyer type potential. The model pseudopotential suggested by Heine and Abarenkov is used for the screened potential. The model parameters are determined from the elastic constants. First we calculate the dispersion curves at 90 °K which agree very well with the neutron scattering data. Then the calculation is extended to the temperature and pressure dependences of dispersion curves. Our result indicates that the phonon frequencies are almost inversely proportional to the volume, a fact which is needed in the Grüneisen equation of state for solids. The martensitic transformation of Na is discussed according to the temperature dependence of the [1 1 10] shear waves along [110] direction. Some related electronic properties such as the Fermi surface distortion and the liquid metal resistivity have also been calculated as a function of pressure.