Vibrational properties of model monatomic crystals under pressure

George Wolf, Raymond Jeanloz

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

The roles of the attractive and repulsive forces in controlling the vibrational properties of monatomic crystals are systematically evaluated as a function of compression. Face-centered-cubic, hexagonal, and body-centered-cubic structures are considered with Lennard-Jones and Buckingham-type interatomic potentials. At zero pressure, the phonon frequencies and their mode-Gr̈neisen parameters deviate strongly from those of a reference state where the atoms interact solely through the corresponding purely repulsive potential. In detail, the degree of deviation depends on the structure, relative range of the repulsive and attractive forces, and the vibrational wavelength. With increasing pressure, the phonon frequencies asymptotically approach values of the purely repulsive reference state. Higher-order properties such as the mode-Gr̈neisen parameters and their logarithmic volume derivatives approach the repulsive limiting values more rapidly than do the frequencies, provided the associated modes do not become unstable. The close-packed lattices are dynamically stable at all positive pressures and display only a small variation among different orders of the frequency spectra Debye moments. However, this variation can be quite large for any structure at strains near that where the lattice is dynamically unstable. We find that the thermal Gr̈neisen parameter decreases with pressure, but the commonly assumed power-law relation of the thermal Gr̈neisen parameter with volume is violated. Average anharmonic vibrational properties are well described by a cell model in these monatomic systems at both low and high pressures. In addition, a strong correlation is found between the static-lattice compressional properties and the average vibrational properties; free-volume relations give good estimates of the high-temperature thermal properties, especially at high pressures.

Original languageEnglish (US)
Pages (from-to)7798-7810
Number of pages13
JournalPhysical Review B
Volume32
Issue number12
DOIs
StatePublished - 1985
Externally publishedYes

Fingerprint

Crystals
crystals
close packed lattices
Free volume
low pressure
thermodynamic properties
Compaction
moments
deviation
Thermodynamic properties
Derivatives
Wavelength
Atoms
estimates
cells
wavelengths
atoms
Temperature
Hot Temperature

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Vibrational properties of model monatomic crystals under pressure. / Wolf, George; Jeanloz, Raymond.

In: Physical Review B, Vol. 32, No. 12, 1985, p. 7798-7810.

Research output: Contribution to journalArticle

Wolf, George ; Jeanloz, Raymond. / Vibrational properties of model monatomic crystals under pressure. In: Physical Review B. 1985 ; Vol. 32, No. 12. pp. 7798-7810.
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