Stability of Ni sites across the pressure-induced insulator-to-metal transition in YNiO3

ALINE Y. RAMOS; CINTHIA PIAMONTEZE; HÉLIO C. N. TOLENTINO; NARCIZO M. SOUZA-NETO; OANA BUNAU; YVES JOLY; STÉPHANE GRENIER; JEAN-PAUL ITIÉ; NÉSTOR E. MASSA; JOSÉ A. ALONSO; MARIA J. MARTINEZ-LOPE

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

American Physical Society

Lugar: Melville; Año: 2012 vol. 88 p. 45102 - 45107

0163-1829

The local environment of nickel atoms in YNiO3 across the pressure-induced insulator-to-metal (IM) transitionwas studied using x-ray absorption spectroscopy (XAS) supported by ab initio calculations. The monotoniccontraction of the NiO6 units under applied pressure observed up to 13 GPa stops in a limited pressure domainaround 14 GPa, before resuming above 16 GPa. In this narrow pressure range, crystallographic modificationsbasically occur in the medium to long range, not in the NiO6 octahedron, whereas the evolution of the near-edgeXAS features can be associated with metallization. Ab initio calculations show that these features are related tomedium-range order, provided that the Ni-O-Ni angle enables a proper overlap of the Ni eg and O 2p orbitals.Metallization is then not directly related to modifications in the average local geometry of the NiO6 units but more likely to an interoctahedral rearrangement. These outcomes provide evidence of the bandwidth-driven nature of the IM transition.