Determination of the thermal properties of AlB2-type WB2

Thermal expansion coefficient of AlB2-type WB2 was investigated using in-situ x-ray diffraction (XRD) measurements and quasi-harmonic Debye approximation combined with density functional theory (DFT) calculations. The calculated average volumetric thermal expansion coefficient 24.86 × 10−6 K−1 agrees with the experimental value 21.52 × 10−6 K−1 in the temperature range of 298 K to 473 K. Different linear thermal expansion coefficients along the a (6.04 × 10−6 K−1) and c (9.39 × 10−6 K−1) directions have been found experimentally. This anisotropic behavior is attributed to the different bonding characteristics along the two directions. A Lindemann-like melting rule has been found for AlB2-type MB2 (M = Ti, Zr, V, Nb, Ta, Cr, Mo and Mn), and the melting point of AlB2-type WB2 has been estimated about 2833.80 ± 18.4 K according to this rule. Furthermore, the temperature and pressure dependence of thermal expansion and heat capacity is also studied. To our knowledge, it is the first time to investigate the thermal properties of AlB2-type WB2.