Ab initio LCAO study of the atomic, electronic and magnetic structures and the lattice dynamics of triclinic CuWO ₄

The electronic, structural and phonon properties of antiferromagnetic triclinic CuWO ₄ have been studied using the first-principles spin-polarized linear combination of atomic orbital (LCAO) calculations based on the hybrid exchange-correlation density functional (DFT)/Hartree-Fock (HF) scheme. In addition, the local atomic structure around both Cu and W atoms has been probed using extended X-ray absorption fine structure (EXAFS) spectroscopy. We show that, by using the hybrid DFT-HF functional, one can accurately and simultaneously describe the atomic structure (the unit cell parameters and the atomic fractional coordinates), the band gap and the phonon frequencies. In agreement with our EXAFS results, the LCAO calculations reproduce a strong distortion of both the CuO ₆ and the WO ₆ octahedra, which occur due to the first-order and second-order Jahn-Teller effects, respectively. We found that the HF admixture of 13-16%, which is implemented in the PBE0-13% and WCGGA-PBE-16% functionals, produces the best result for CuWO ₄. The calculated properties agree well with the available experimental data provided by diffraction, optical, X-ray photoelectron and Raman spectroscopies.