Hybrid-Density Functional Calculations of Structural, Electronic, Magnetic, and Thermodynamic Properties of α-Cu2P2O7

Abstract

We present a comparative study (using PBE, PBE0, and HSE functionals) of electronic and atomic structure, magnetism, and phonon dispersion relations of (Formula presented.) -Cu (Formula presented.) P (Formula presented.) O (Formula presented.). Four possible magnetic configurations are considered, FM, AFM-1, AFM-2, and AFM-3. The calculations reveal that (Formula presented.) -Cu (Formula presented.) P (Formula presented.) O (Formula presented.) is mechanically and thermodynamically stable. The elastic moduli indicate a weak resistance of the compound to volume and shear deformations. The electronic structure at the valence band maximum is dominated by O, with a small admixture of Cu- (Formula presented.) states. The conduction band results from the hybridization between Cu and O states which, in the case of AFM-2, produces the largest band gap of 3.966 eV and the smallest magnetic moment of ±0.785 (Formula presented.) on Cu. AFM-2 is found to be the lowest-energy structure that may be viewed as consisting of quasi-one-dimensional −Cu (Formula presented.) Cu (Formula presented.) Cu (Formula presented.) Cu (Formula presented.) chains along the b axis; the antiferromagnetism is due to two identical Cu−O−Cu paths with a bond angle of 100.301 (Formula presented.). The phonon spectra exhibit four distinct frequency ranges corresponding to different vibrational modes of ions and ionic groups. Thus, a quantitative description of the structural, electronic, and magnetic properties of (Formula presented.) -Cu (Formula presented.) P (Formula presented.) O (Formula presented.) is possible using the HSE hybrid functional, which enables computational studies of transition metal pyro compounds.