Charge disproportionation and the pressure-induced insulator?metal transition in cubic perovskite PbCrO3

JINGUANG CHENG; K. E. KWEON; S. A. LARREGOLA; YANG DING; Y. SHIRAKO; L. G. MARSHALL; Z.-Y. LI; X. LI; ANTÓNIO M. DOS SANTOS; M. R. SUCHOMEL; K. MATSUBAYASHI; Y. UWATOKO; G. S. HWANG; JOHN B. GOODENOUGH; J.-S. ZHOU

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA

NATL ACAD SCIENCES

Año: 2014 vol. 112

0027-8424

The perovskite PbCrO3 is an antiferromagnetic insulator. However, the fundamental interactions leading to the insulating state in this single-valent perovskite are unclear. Moreover, the origin of the unprecedented volume drop observed at a modest pressure of P = 1.6 GPa remains an outstanding problem. We report a variety of in situ pressure measurements including electron transport properties, X-ray absorption spectrum, and crystal structure study by X-ray and neutron diffraction. These studies reveal key information leading to the elucidation of the physics behind the insulating state and the pressure-induced transition. We argue that a charge disproportionation 3Cr4+ → 2Cr3+ + Cr6+ in association with the 6s-p hybridization on the Pb2+ is responsible for the insulating ground state of PbCrO3 at ambient pressure and the charge disproportionation phase is suppressed under pressure to give rise to a metallic phase at high pressure. The model is well supported by density function theory plus the correlation energy U (DFT+U) calculations.