报告题目：非中心对称氧化物/氟化物低温合成
        Low temperature synthesis of (noncentrosymmetric) oxide-fluorides
报告内容简介：The design and discovery of novel noncentrosymmetric materials – materials that lack an inversion center – with large second-order dielectric responses, χ(2), that efficiently achieve frequency conversion has been a long-standing and difficult goal of inorganic chemistry. Recently, nanolithography has sought UV lasers to create increasingly small lithographic features. To pursue UV lasers, scientists have sought new SHG active crystals to double the frequency of laser light to higher energies. One such material is the oxide-fluoride KBe2BO3F2. Professor Chen’s Anionic Group Theory has established that efficient SHG-active crystals often have anions with aligned polar moments in the solid state. Therefore, to synthesize highly-efficient SHG crystals, a promising strategy is to utilize anions that inherently contain polar moments. For this reason, our group has examined oxide-fluoride early transition materials; the d0 early transition metal cations undergo out-of-center distortions owing to electronic effects (specifically Second-Order Jahn-Teller distortions). These polar distortions are observed in oxide-fluoride anions of the cations vanadium (V5+), niobium (Nb5+), tantalum (Ta5+), molybdenum (Mo6+) and tungsten (W6+). In 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 octahedra. The 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 bond. The additional valence thus creates stronger M=O bonds within the anions of the solid state compound and thus a stronger distortion. Our syntheses of numerous inorganic and organic-inorganic hybrid oxide-fluoride phases have allowed the analysis of the electronic environments of the early transition metal polyhedra; the distortions of the anions and non-spherical electronic environments have allowed us to synthesize non-centrosymmetric materials and establish principles and guidelines to target syntheses of SHG-active materials.

 

报告人姓名：Kenneth R. Poeppelmeier

 

报告人简介：Kenneth R. Poeppelmeier 美国西北大学教授 美国西北大学催化与表面科学中心主任 美国西北大学超导科学与技术中心副主任 美国化学会“无机化学”副主编 美国化学会无机化学与固态化学分会主席 美国“合金与化合物”编委
报告人简介(英文)：Kenneth R. Poeppelmeier Charles E. & Emma H. Morrison Professor of Chemistry Director of Center for Catalysis and Surface Science Associate Director, Northwestern University Science and Technology Center for Superconductivity Associate Editor, Inorganic Chemistry Chair, American Chemical Society Division of Inorganic Chemistry & Solid-State Chemistry Editorial Boards, Journal of Alloys and Compounds,
报告人单位：美国西北大学催化与表面科学中心
     Center for Catalysis and Surface Science，Northwestern University, USA
报告时间：2014-03-07 09:30
报告地点：上海大学材料学院（宝山校区）材料楼520会议室
主办单位：上海大学材料学院