Phonon contributions to the entropies of hP24 and fcc Co{sub 3}V

Journal Article · Fri Oct 01 04:00:00 EDT 1999 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.60.9329· OSTI ID:686562

Robertson, J L ^[1]; Fultz, B; Frase, H N ^[2]

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1. Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831 (United States)
2. Keck Laboratory of Engineering Materials, Mail 138-78, California Institute of Technology, Pasadena, California 91125 (United States)

Inelastic neutron-scattering spectra and neutron-diffraction patterns were measured on the alloy Co{sub 3}V at temperatures from 1073{endash}1513 K, where the hP24 (ordered hexagonal) and fcc structures are the equilibrium states of the alloy. Phonon density of states (DOS) curves were calculated from the inelastic-scattering spectra, allowing estimates of the vibrational entropy in the harmonic and quasiharmonic approximations. The vibrational entropy of the hP24{endash}fcc phase transition at 1323 K was found to be 0.07k{sub B}/atom. The anharmonic contributions to the entropy over a temperature range of 100 K were comparable to the vibrational entropy of this phase transition. The anharmonic softening of the phonon DOS was only slightly larger for the hP24 than the fcc phase, however, so the anharmonic effects contribute only slightly to the difference in entropy of the two phases. The simple Gr{umlt u}neisen approximation was inadequate for predicting the thermal softening of the phonon DOS. {copyright} {ital 1999} {ital The American Physical Society}

• OSTI ID: 686562
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 13 Vol. 60; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COBALT ALLOYS
COBALT BASE ALLOYS
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
ENERGY-LEVEL DENSITY
ENTROPY
FCC LATTICES
GRUENEISEN CONSTANT
LATTICE VIBRATIONS
NEUTRON DIFFRACTION
PHONONS
TEMPERATURE RANGE 1000-4000 K
VANADIUM ALLOYS