We examine the insulator-to-metal transition taking place in ${\mathrm{NaOsO}}_3$, a Slater insulator, under pressure. While an antiferromagnetic metallic phase is absent in Slater's picture, we find a robust phase present with a high ordering temperature. This is traced to the negative charge transfer energy regime to which the system belongs. The band gap is found to have a weak pressure dependence, an order of magnitude smaller than other known materials. This follows from the unusual $d$ filling to which Os corresponds, with the antiferromagnetism favoring the insulating state. Consequently, the pressure-dependent bond length decrease and the bond angle variations compete in minimizing the changes in the effective hopping between the Os sites, leading to a “persistent insulating” state.

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• Magnetism
• Pressure effects
• Antiferromagnets
• Magnetic insulators
• Density functional calculations