Realizing ultra-low thermal conductivity by strong synergy of asymmetric geometry and electronic structure in boron nitride and arsenide

The design of novel devices with specific technical interests through modulating structural properties and bonding characteristics promotes the vigorous development of materials informatics.Boron arsenide and boron nitride,as remarkably high thermal conductivity(κ)materials,are unfavorable for thermal insulation applications as well as thermoelectric devices.In this study,based on first-principles calculations,we identify a group of novel borides with ultra-low κ,i.e.,g-B3X5(X=N,P,and As).The κ of g-B3N5,g-B3P5,and g-B3As5are 21.08,2.50,and 1.85 W·m-1·K-1,respectively,which are boron nitride and boron arsenide systems with the lowest κ reported so far.The ultra-low κ is attributed to the synergy effect of electronics(lone-pair electrons) and geometry(buckling structures) on thermal transport.The discovery of the ultralow κ of boron nitride and boron arsenide systems can well fill the gaps in applications of thermal insulation and thermoelectric devices.