The layered metal phosphorous trisulfide ${\mathrm{FePS}}_3$ is reported to be a Mott insulator at ambient conditions and to undergo structural and insulator-metal phase transitions under pressure. However, the character of the resulting metallic states has not been understood clearly so far. Here, we theoretically study the phase transitions of ${\mathrm{FePS}}_3$ using first-principles methods based on density functional theory and embedded dynamical mean field theory. We find that the Mott transition in ${\mathrm{FePS}}_3$ can be orbital selective, with $t_{2g}$ states undergoing a correlation-induced insulator-to-metal transition while $e_g$ states remain gapped. We show that this orbital-selective Mott phase, which occurs only when nonhydrostatic pressure is used, is a bad metal (or non-Fermi liquid) with large fluctuating moments due to Hund's coupling. Further application of pressure increases the crystal-field splitting and converts the system to a conventional Fermi liquid with low-spin configurations dominant. Our results show that ${\mathrm{FePS}}_3$ is an example of a system that realizes an orbital-selective Mott phase, allowing tuning between correlated and uncorrelated metallic properties in an accessible pressure range ($\le 18$ GPa).

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• First-principles calculations
• Metal-insulator transition
• Iron-based superconductors
• Mott insulators
• Density functional theory
• Dynamical mean field theory
• Non-Fermi-liquid theory