Ultrahigh-pressure structural phase transitions in Cr, Mo, and W

Journal Article · Sat Feb 01 04:00:00 EST 1992 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.45.2004· OSTI ID:5007351

Moriarty, J A ^[1]

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1. Lawrence Livermore National Laboratory, University of California, Livermore, California 94550 (United States)

On the basis of first-principles total-energy calculations, we predict the ultrahigh-pressure destabilization of the bcc structure in the group-VIB elements Cr, Mo, and W through a bcc{r arrow}hcp phase transition at pressures of about 7.0, 4.2, and 12.5 Mbar, respectively. In Mo and W, a subsequent hcp{r arrow}fcc transition is also predicted at about 6.2 and 14.4 Mbar, respectively. The overall driving mechanism for these transitions is a continuous {ital sp}{r arrow}{ital d} transfer of electrons upon compression, although other factors play an important quantitative role, especially the hard-core-like interaction between the large cores of these elements, which disfavors the bcc structure and serves to lower the bcc{r arrow}hcp transition pressures. While the actual predicted transition pressures are sensitive to the details of the calculations, the qualitative trends are not, and the bcc{r arrow}hcp transition in Mo should be within reach of static diamond-anvil-cell experiments. In this regard, we have also calculated accurate 300-K isotherms for bcc Cr, Mo, and W valid up to the 5--6-Mbar pressure range.

• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5007351
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 45:5; ISSN 0163-1829; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
BCC LATTICES
CHROMIUM
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
CUBIC LATTICES
ELEMENTS
FCC LATTICES
HCP LATTICES
HEXAGONAL LATTICES
ISOTHERMS
METALS
MOLYBDENUM
PHASE TRANSFORMATIONS
PRESSURE EFFECTS
TRANSITION ELEMENTS
TUNGSTEN
VERY HIGH PRESSURE