Elastic Properties across the y→α Volume Collapse in Cerium versus Pressure and Temperature
Journal Article
·
· Nature Communications
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Carnegie Institute of Washington, Argonne, IL (United States)
Here, the longitudinal and transverse sound speeds, cL and cT, of polycrystalline cerium were measured isothermally vs pressure up to the critical temperature across the iso-structural γ-α volume collapse (VC) phase transition. We deduce values for the adiabatic bulk modulus BS, the shear modulus G = ρcT2, the Poisson’s ratio ν and the Debye temperature, θD(p). We find that the elastic constant C12 is solely responsible for the decrease of BS with pressure towards the VC at RT. With increasing temperature, the lattice contribution ΔSvib(γ→α) to the total entropy change across the VC decreases more rapidly to zero than the total entropy itself suggesting that another mechanism, possibly disorder, assists in stabilizing the γ-phase entropically against the α-phase. Also, with increasing temperature, the Poisson’s ratio becomes negative near the VC transition, meaning that cerium metal takes on auxetic characteristics over a small pressure range. At the critical point the Poisson’s ratio ought to be -1, since the isothermal bulk modulus vanishes and the shear modulus remains nonzero.
- Research Organization:
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- AC52-07NA27344
- OSTI ID:
- 1410020
- Alternate ID(s):
- OSTI ID: 1408129
- Report Number(s):
- LLNL-JRNL--677515
- Journal Information:
- Nature Communications, Journal Name: Nature Communications Vol. 8; ISSN 2041-1723
- Publisher:
- Nature Publishing GroupCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Anharmonicity-induced first-order isostructural phase transition of zirconium under pressure
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journal | December 2018 |
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