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We report on XANES and EXAFS measurements of SmNiO3 from 20 K to 600 K and upto 38 GPa at the Ni K- and Sm L3- edges. A multiple component pre- Ni K-edgetail is understood originating from 1s transitions to 3d-4p states while apost-edge shoulder increases distinctively smooth, at about the insulator tometal phase transition (TIM), due to the reduction of electron-phononinteractions as the Ni 3d and O 2p band overlap triggers the metallic phase.This effect is concomitant with pressure induced Ni-O-Ni angle incrementstoward more symmetric Ni3+ octahedra of the rhombohedral R-3c space group. Roomtemperature pressure dependent Ni white line peak energies have an abrupt~3.10+-0.04 GPa Pa valence discontinuity from non-equivalent Ni3+{\delta} +Ni3-{\delta} charge disproportionate net unresolved absorber turning at ~TIMinto Ni3+ of the orthorhombic Pbnm metal oxide phase. At 20 K the overall whiteline response, still distinctive at TIM ~8.1+-0.6 GPa is much smoother due tolocalization. Octahedral bond contraction up to 38 GPa and at 300 K and 20 Kshow breaks in its monotonic increase at the different structural changes. TheSm L3-edge does not show distinctive behaviors either at 300 K or 20 K up about35 GPa but the perovskite Sm cage, coordinated to eight oxygen atoms, undergoesstrong uneven bond contractions at intermediate pressures where we foundcoexistence of octahedral and rhombohedral superexchange angle distortions. Wefound that the white line pressure dependent anomaly may be used as an accuratealternative for delineating pressure-temperature phase diagrams.

Temperature and high-pressure dependent X-ray absorption of SmNiO3 at the Ni K- and Sm L3- edges