Thinking about Noncentrosymmetric Materials
作者单位：Department of ChemistryNorthwestern University
会议名称：《第十四届固态化学与无机合成学术会议》
会议日期：2016年
学科分类：12[管理学] 08[工学] 0805[工学-材料科学与工程（可授工学、理学学位）] 080502[工学-材料学]
摘 要：The design of noncentrosymmetric materials-materials that lack an inversion center-with large second-order dielectric responses,χ(2),and which efficiently achieve frequency conversion,has been a long-standing and difficult problem for organic and inorganic ***,nanolithography has sought UV lasers to create increasingly small lithographic *** pursue UV lasers,we seek new SHG active crystals to double the frequency of laser light to higher *** Chen’s Anionic Group Theory has established that efficient SHG-active crystals often have anions with aligned polar moments in the solid ***,to synthesize highly-efficient SHG crystals,a promising strategy is to utilize anions that inherently contain polar moments such as the oxide-fluoride KBeBOF(KBBF),discovered in the Chen *** this reason,our group has examined early transition metal cations with mixed oxidefluoride *** polar distortions are observed in metal oxide-fluoride anions containing the cations vanadium(V),niobium(Nb),tantalum(Ta),molybdenum(Mo) and tungsten(W).Owing to electronic effects,specifically Second-Order Jahn-Teller(SOJT) distortions,these d early transition metal cations undergo large out-of-center *** oxide phases of these metals,the Second-Order Jahn-Teller distortion is directed towards oxide ligand(s) of corner,edge,or face(s) of the anionic *** use of oxide-fluoride compounds enhances the distortion of the anion as the metal-fluoride bonds contain less valence than would exist for metal-oxide *** additional valence thus creates stronger M=O bonds and thus a stronger *** numerous inorganic and organic-inorganic hybrid oxide-fluoride phases,with their distortions and non-spherical electronic environments,help establish principles and guidelines to target more generally SHG-active materials.