A new low temperature modification of TaTe2—Comparison to the room temperature and the hypothetical 1T-TaTe2 modification

A new low temperature modification of TaTe2 is reported (structural data at T = 150 K: C2/m (no. 12), Z = 18, a = 14.792(1) Å, b = 10.8829(9) Å, c = 9.3005(7) Å, β = 110.693(1)°). Temperature dependent single crystal X-ray diffraction, magnetic susceptibility, resistivity, specific heat capacity and differential scanning calorimetry measurements all show a phase transition at TPT ≈ 170 K. The structural change is mainly reflected by a shift of only 2/9 of the Ta atoms by 0.283 Å, which leads to clustering of the Ta atoms. The bonding patterns were derived from the Crystal Orbital Hamiltonian Population and from the Electron Localization Function based on Density Functional Theory calculations, respectively. Differences to the room temperature modification and to the hypothetical 1T-TaTe2 structure are elaborated. It is suggested, that the room temperature structure might show a dynamic type of disorder, with the X-ray structure analysis reflecting the time averaged structure.