First-principles study of structural, elastic, and bonding properties of pyrochlores

Abstract

Density Functional Theory calculations have been performed to obtain lattice parameters, elastic constants, and electronic properties of ideal pyrochlores with the composition A${}_2$B${}_2$O${}_7$ (where A=La,Y and B=Ti,Sn,Hf, Zr). Some thermal properties are also inferred from the elastic properties. A decrease of the sound velocity (and thus, of the Debye temperature) with the atomic mass of the B ion is observed. Static and dynamical atomic charges are obtained to quantify the degree of covalency/ionicity. A large anomalous contribution to the dynamical charge is observed for Hf, Zr, and specially for Ti. It is attributed to the hybridization between occupied $2p$ states of oxygen and unoccupied d states of the B cation. The analysis based on Mulliken population and deformation charge integrated in the Voronoi polyhedra indicates that the ionicity of these pyrochlores increases in the order Sn--Ti--Hf--Zr. The charge deformation contour plots support this assignment.

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References in corpus (3)

• The SIESTA method for ab initio order-N materials simulation
• Efficient index handling of multidimensional periodic boundary conditions
• Strong-correlation effects in Born effective charges

Cited by in corpus (6)

• Investigation of the magnetic structure and crystal field states of pyrochlore antiferromagnet Nd2Zr2O7
• Topological phases in layered pyrochlore oxide thin films along the [111] direction
• First principles calculation and experimental investigation of lattice dynamics in the rare earth pyrochlores R2Ti2O7 (R=Tb, Dy, Ho)
• Structural, optical and mechanical properties of Y2Ti2O7 single crystal
• New high-pressure phase and equation of state of Ce2Zr2O8
• Spin-lattice Coupling in U(1) Quantum Spin Liquids