Angular forces and melting in bcc transition metals: A case study of molybdenum
- Lawrence Livermore National Laboratory, University of California, Livermore, California 94551 (United States)
Both the multi-ion and effective pair potentials also permit a large amount of supercooling of the liquid before the onset of freezing. With [ital v][sub 2][sup eff] a bcc structure is nucleated at freezing, while with the multi-ion potentials an amorphous glasslike structure is obtained, which appears to be related to the energetically competitive [ital A]15 structure. In our second approach to melting, the multi-ion potentials have been used to obtain accurate solid and liquid free energies from quasiharmonic lattice dynamics and MD calculations of thermal energies and pressures. The resulting ion-thermal melting curve exactly overlaps the dynamically observed melting point, indicating that no superheating of the solid occurred in our MD simulations. To obtain a full melting curve, electron-thermal contributions to the solid and liquid free energies are added in terms of the density of electronic states at the Fermi level, [rho]([ital E][sub [ital F]]). Here the density of states for the solid has been calculated with the linear-muffin-tin-orbital method, while for the liquid tight-binding calculations have been used to justify a simple model. In the liquid [rho]([ital E][sub [ital F]]) is increased dramatically over the bcc solid, and the net effect of the electron-thermal contributions is to lower the calculated melting temperatures by about a factor of 2. A full melting curve to 2 Mbar has thereby been obtained and the calculated melting properties near zero pressure are in generally good agreement with experiment.
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 5094439
- Journal Information:
- Physical Review, B: Condensed Matter; (United States), Vol. 49:18; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
MOLYBDENUM
MELTING POINTS
TRANSITION ELEMENTS
BCC LATTICES
FERMI LEVEL
INTERATOMIC FORCES
MOLECULAR ORBITAL METHOD
MUFFIN-TIN POTENTIAL
CALCULATION METHODS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CUBIC LATTICES
ELEMENTS
ENERGY LEVELS
METALS
PHYSICAL PROPERTIES
POTENTIALS
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
360102* - Metals & Alloys- Structure & Phase Studies
665000 - Physics of Condensed Matter- (1992-)