First-principles investigation of ferroelectric and piezoelectric properties in one-dimensional transition metal oxytetrahalides

We perform first-principles density functional theory calculations to systematically investigate electronic structures of a quasi-one-dimensional $M\mathrm{O}{X}_{4}$ ($M=\mathrm{Cr},\mathrm{Mo},\mathrm{W}$, and $X=\mathrm{F},\mathrm{Cl},\mathrm{Br}$) materials consisting of weakly coupled one-dimensional chains. The compositional dependence on the ferroelectric and piezoelectric properties such as switching polarization, energy barriers, Born effective charges, and piezoelectric coefficients are investigated. We find that the majority of the $M\mathrm{O}{X}_{4}$ systems exhibit sizable polarization and large piezoelectric coefficients comparable to conventional ferroelectrics. More importantly, we find that the energy cost of forming a ${180}^{\ensuremath{\circ}}$ domain walls is negligibly small due to the weak interchain coupling, having an atomically thin domain wall with almost no reduction in the local polarization. The robust ferroelectric switching, atomically thin ferroelectric domain wall, and large piezoelectric coefficients make the $M\mathrm{O}{X}_{4}$ family of materials potential candidates for applications for efficient electronic devices such as high-density ferroelectric memories and high-resolution pressure sensors.