Ternary pentagonal BXN (X = C, Si, Ge, and Sn) sheets with high piezoelectricity

Abstract

The discovery of new and stable two-dimensional pentagonal materials with piezoelectric properties is essential for technological advancement. Inspired by recently reported piezoelectric materials <i>penta</i>-BCN and <i>penta</i>-BSiN, we proposed <i>penta</i>-BGeN and <i>penta</i>-BSnN as new members of the <i>penta</i>-family based on first-principles calculations. Comprehensive analyses indicated that both <i>penta</i>-BGeN and <i>penta</i>-BSnN are thermodynamically, dynamically, mechanically, and thermally stable. In terms of mechanical stability, the elastic constant decreased as lower elements in group 4A of the periodic table were used. Therefore, <i>penta</i>-BGeN and <i>penta</i>-BSnN are softer than <i>penta</i>-BCN and <i>penta</i>-BSiN. In terms of piezoelectric properties, piezoelectric stress and strain tensors increase following the same pattern. In group 4A, <i>penta</i>-BSnN had the highest intrinsic piezoelectricity, especially the <i>e</i> ₂₂ piezoelectric stress. Typically, the piezoelectric strain <i>d</i> _<i>ij</i> coefficient increases with material softness; <i>penta</i>-BSnN possessed the highest <i>d</i> _<i>ij</i> . Thus, due to its inherent piezoelectricity, <i>penta</i>-BSnN has tremendous potential as a nanoscale piezoelectric material.