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Title: Angular forces and melting in bcc transition metals: A case study of molybdenum

Abstract

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 lowermore » 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.« less

Authors:
 [1]
  1. Lawrence Livermore National Laboratory, University of California, Livermore, California 94551 (United States)
Publication Date:
OSTI Identifier:
5094439
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Journal Article
Journal Name:
Physical Review, B: Condensed Matter; (United States)
Additional Journal Information:
Journal Volume: 49:18; Journal ID: ISSN 0163-1829
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 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-)

Citation Formats

Moriarty, J A. Angular forces and melting in bcc transition metals: A case study of molybdenum. United States: N. p., 1994. Web. doi:10.1103/PhysRevB.49.12431.
Moriarty, J A. Angular forces and melting in bcc transition metals: A case study of molybdenum. United States. doi:10.1103/PhysRevB.49.12431.
Moriarty, J A. Sun . "Angular forces and melting in bcc transition metals: A case study of molybdenum". United States. doi:10.1103/PhysRevB.49.12431.
@article{osti_5094439,
title = {Angular forces and melting in bcc transition metals: A case study of molybdenum},
author = {Moriarty, J A},
abstractNote = {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.},
doi = {10.1103/PhysRevB.49.12431},
journal = {Physical Review, B: Condensed Matter; (United States)},
issn = {0163-1829},
number = ,
volume = 49:18,
place = {United States},
year = {1994},
month = {5}
}