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Title: Elastic Properties across the y→α Volume Collapse in Cerium versus Pressure and Temperature

Here, the longitudinal and transverse sound speeds, c L and c T, 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 = ρc T 2, the Poisson’s ratio ν and the Debye temperature, θ D(p). We find that the elastic constant C 12 is solely responsible for the decrease of B S with pressure towards the VC at RT. With increasing temperature, the lattice contribution ΔS vib(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.
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [2] ;  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Carnegie Institute of Washington, Argonne, IL (United States)
Publication Date:
Report Number(s):
LLNL-JRNL-677515
Journal ID: ISSN 2041-1723
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 8; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
OSTI Identifier:
1410020

Lipp, M. J., Jenei, Zs., Cynn, H., Kono, Y., Park, C., Kenney-Benson, C., and Evans, W. J.. Elastic Properties across the y→α Volume Collapse in Cerium versus Pressure and Temperature. United States: N. p., Web. doi:10.1038/s41467-017-01411-9.
Lipp, M. J., Jenei, Zs., Cynn, H., Kono, Y., Park, C., Kenney-Benson, C., & Evans, W. J.. Elastic Properties across the y→α Volume Collapse in Cerium versus Pressure and Temperature. United States. doi:10.1038/s41467-017-01411-9.
Lipp, M. J., Jenei, Zs., Cynn, H., Kono, Y., Park, C., Kenney-Benson, C., and Evans, W. J.. 2017. "Elastic Properties across the y→α Volume Collapse in Cerium versus Pressure and Temperature". United States. doi:10.1038/s41467-017-01411-9. https://www.osti.gov/servlets/purl/1410020.
@article{osti_1410020,
title = {Elastic Properties across the y→α Volume Collapse in Cerium versus Pressure and Temperature},
author = {Lipp, M. J. and Jenei, Zs. and Cynn, H. and Kono, Y. and Park, C. and Kenney-Benson, C. and Evans, W. J.},
abstractNote = {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.},
doi = {10.1038/s41467-017-01411-9},
journal = {Nature Communications},
number = ,
volume = 8,
place = {United States},
year = {2017},
month = {10}
}