Electronic, dynamical, and thermal properties of ultra-incompressible superhard rhenium diboride: A combined first-principles and neutron scattering study

Rhenium diboride is a recently recognized ultra-incompressible superhard material. Here we report the electronic (e), phonon (p), e-p coupling, and thermal properties of ReB2 from first-principles densityfunctional theory calculations and neutron scattering measurements. Our calculated elastic constants (c11 =641 GPa, c12=159 GPa, c13=128 GPa, c33=1037 GPa, and c44=271 GPa), bulk modulus (B≈350 GPa) and hardness (H≈46 GPa) are in good agreement with the reported experimental data. The calculated phonon density of states agrees very well with our neutron vibrational spectroscopy result. Electronic and phonon analysis indicates that the strong covalent B-B and Re-B bonding is the main reason for the super incompressibility and hardness of ReB2. The thermal expansion coefficients, calculated within the quasiharmonic approximation and measured by neutron powder diffraction, are found to be nearly isotropic in a and c directions and only slightly larger than that of diamond in terms of magnitude. The excellent agreement found between calculations and experimental measurements indicate that first-principles calculations capture the main interactions in this class of superhard materials, and thus can be used to search, predict, and design new materials with desired properties. Disciplines Engineering | Materials Science and Engineering Comments Suggested Citation: Zhou, W., Wu, H. and Yildirim, T. (2007). Electronic, dynamical, and thermal properties of ultraincompressible superhard rhenium diboride: A combined first-principles and neutron scattering study. Physical Review B. 76, 184113. © 2007 The American Physical Society http://dx.doi.org/10.1103/PhysRevB.76.184113 This journal article is available at ScholarlyCommons: http://repository.upenn.edu/mse_papers/201 Electronic, dynamical, and thermal properties of ultra-incompressible superhard rhenium diboride: A combined first-principles and neutron scattering study W. Zhou,1,2,* H. Wu,1,3 and T. Yildirim1,2 1NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA 2Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA 3Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA Received 27 August 2007; published 19 November 2007 Rhenium diboride is a recently recognized ultra-incompressible superhard material. Here we report the electronic e , phonon p , e-p coupling, and thermal properties of ReB2 from first-principles densityfunctional theory calculations and neutron scattering measurements. Our calculated elastic constants c11 =641 GPa, c12=159 GPa, c13=128 GPa, c33=1037 GPa, and c44=271 GPa , bulk modulus B 350 GPa and hardness H 46 GPa are in good agreement with the reported experimental data. The calculated phonon density of states agrees very well with our neutron vibrational spectroscopy result. Electronic and phonon analysis indicates that the strong covalent B-B and Re-B bonding is the main reason for the super incompressibility and hardness of ReB2. The thermal expansion coefficients, calculated within the quasiharmonic approximation and measured by neutron powder diffraction, are found to be nearly isotropic in a and c directions and only slightly larger than that of diamond in terms of magnitude. The excellent agreement found between calculations and experimental measurements indicate that first-principles calculations capture the main interactions in this class of superhard materials, and thus can be used to search, predict, and design new materials with desired properties. DOI: 10.1103/PhysRevB.76.184113 PACS number s : 71.20. b, 62.20.Dc, 63.20. e, 65.40. b