Structural investigation of Np2Co17 and analogue compounds under pressure

The structural behavior of Np2Co17 is investigated by means of high-pressure diamond-anvil compression measurements and is compared with that of the isostructural compounds Lu2Co17 and Lu2Ni17. The Th2Ni17-type hexagonal crystal structure is preserved with no measurable discontinuous volume collapses up to the highest achieved pressure, p = 43 GPa. For Np2Co17, fits to the Birch-Murnaghan and Vinet equations of state give values of the isothermal bulk modulus and its pressure derivative of B0 = 286 GPa and B 0= 3, revealing that this Np compound is a highly incompressible solid with stiffness comparable to that of superhard covalently bonded materials. For the Lu2T17 (T = Co, Ni) compounds, the measured bulk modulus changes from B0 = 137 GPa for T = Co to B0 = 257 GPa for T = Ni. The isothermal equation of state for the studied compounds are in excellent agreement with the results of ab initio fully relativistic, full-potential local spin-density functional calculations. Theoretical estimates of the bulk modulus are given also for Np2Ni17, for which B0 is predicted to assume values intermediate between those measured for Lu2Ni17 and Np2Co17.

HEN Amir;  HEATHMAN Stephen;  ELOIRDI Rachel;  GRIVEAU Jean-Christophe;  ELGAZZAR S.;  OPPENEER P.M.;  HALEVY Itzhak;  ORION I.;  CACIUFFO Roberto; 

2014-08-28

AMER PHYSICAL SOC

JRC89451

1098-0121,   

http://journals.aps.org/prb/abstract/10.1103/PhysRevB.90.054107,    https://publications.jrc.ec.europa.eu/repository/handle/JRC89451,   

10.1103/PhysRevB.90.054107,