Possible antiferroelectric-to-ferroelectric transition and metallic antiferroelectricity caused by charge doping in PbZrO3

Using linear-response density functional calculations we study how the soft modes at both the zone center and the zone boundary are influenced by charge doping in cubic $\mathrm{Pb}\mathrm{Zr}{\mathrm{O}}₃$. We find (i) upon the electron doping of $n=\ensuremath{-}0.5$ per unit cell, the soft-mode frequency at zone-center $\mathrm{\ensuremath{\Gamma}}$ becomes considerably lower than that at the zone-boundary $R$, showing that electron doping may turn antiferroelectric $\mathrm{Pb}\mathrm{Zr}{\mathrm{O}}₃$ into ferroelectric. (ii) On the other hand, when the hole is doped into $\mathrm{Pb}\mathrm{Zr}{\mathrm{O}}₃$, the soft mode at $R$ or $M$ remains to be the lowest in frequency, and therefore antiferroelectric instability is robust and persists after hole doping. Since hole doping makes $\mathrm{Pb}\mathrm{Zr}{\mathrm{O}}₃$ metallic, the coexistence of metallicity and antiferroelectricity demonstrates the feasibility of metallic antiferroelectricity. (iii) Electron doping and hole doping are revealed to impact the atom-atom interaction very differently. The origin responsible for these charge-doping phenomena is provided.