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铅/铋硼酸盐中孤对电子对非线性光学效应及带隙的影响机制研究
李丹妮
学位类型硕士
导师杨志华
2016-05-26
学位授予单位中国科学院大学
学位授予地点北京
学位专业材料工程
关键词孤对电子效应 第一性原理 立构活性 带隙 倍频
摘要

摘要非线性光学晶体材料是激光技术的核心材料。目前随着光电子产业及激光技术发展,在紫外/深紫外波段仍需要倍频效应较大、紫外截止边较低的非线性光学晶体材料。通常情况下,为了增大晶体材料的倍频效应会在硼酸盐等在紫外具有优势的氧酸盐体系中引入一些非中心的结构单元:d0电子构型的过渡金属离子,或含孤对电子阳离子Pb2+,Bi3+等。然而引入以上非中心基元将可能导致紫外截止边红移,从而不利于获得紫外用非线性光学晶体材料。因此,如何平衡紫外截止边(对应带隙)与倍频效应矛盾关系成为非线性光学研究领域亟待解决的一个课题。本文主要以含孤对电子阳离子Pb2+,Bi3+的硼酸盐为研究体系,基于密度泛函理论的第一性原理计算对含孤对电子硼酸盐进行了机理研究,从吸收边的红移以及倍频效应来源两个方面入手讨论孤对电子阳离子效应对化合物光学性质的影响,以揭示带隙与倍频的平衡关系。1) 为探索含孤对电子阳离子对带隙(截止边)红移,以含铅硼酸盐及铅-碱土金属替换后钡硼酸盐同构化合物为研究目标。筛选出一系列具有代表性的铅硼酸盐Pb2B5O9Cl、Ba2Pb(B3O6)2、BaPb[B5O9(OH)]·H2O,及其同构钡硼酸盐Ba2B5O9Cl、Ba3(B3O6)2、Ba2[B5O9(OH)]·H2O,其中化合物Ba2[B5O9(OH)]·H2O,Ba3(B3O6)2是通过模拟计算所得的虚拟化合物。计算了其电子结构,比对化合物的带隙,发现Pb2B5O9Cl相对Ba2B5O9Cl的带隙红移较大,而Ba2Pb(B3O6)2、BaPb[B5O9(OH)]·H2O相对其同构碱土金属硼酸盐Ba3(B3O6)2、Ba2[B5O9(OH)]·H2O的带隙红移较小。对比铅-氧与钡-氧相互作用发现,铅硼酸盐相对其同构碱土金属硼酸盐的截止边红移程度与孤对电子阳离子立构活性程度呈正关联行为,此外铅氧多面体畸变程度与立构活性大小有一致的趋势。同时,运用倍频密度方法对BaPb[B5O9(OH)]·H2O的倍频来源进行分析,倍频密度图显示化合物BaPb[B5O9(OH)]·H2O中铅原子对化合物的倍频效应有贡献。通过对一系列铅硼酸盐及其碱土金属硼酸盐的研究,为实验的合成提供新的理论指导。2) 为了探索孤对电子阳离子倍频效应增益机制,调研一系列铅硼酸盐以及其同构碱土金属硼酸盐,Pb2B5O9Cl,Pb3B6O11F2,Pb2Ba3(BO3)3Cl,Ba2B5O9Cl,Ba3B6O11F2,Ba5(BO3)3Cl。同时通过理论模拟计算得到其态密度图及倍频密度图,结果显示,当铅硼酸盐中铅的立构活性较强时,其对应的倍频增益越大。3) 基于铅氧与铋氧立构化学立构活性模型形成的相似性,我们利用密度泛函理论进一步研究了一系列铋硼酸盐Bi2B8O15,BiB3O6,BiB2O4F和CaBi2B2O7。根据计算结果对比电子结构,我们发现Bi2B8O15具有较弱的立构活性。同时态密度图显示在费米面附近Bi、O占据重要角色,对倍频效应有贡献。此外,我们采用了实空间原子切割方法,研究Bi-O基团对倍频效应的贡献,证明Bi孤对电子阳离子的引入对倍频效应有较大贡献。通过理论模拟计算,调研一系列铋硼酸盐,筛选出具有较大带隙合适倍频效应的铋硼酸盐化合物Bi2B8O15,合成化合物Bi2B8O15并首次表征其光学性质。

其他摘要

AbstractWith the development of laser technology, nonlinear optical materials act an increasingly important role. In order to meet the development needs, people continue to explore nonlinear materials with high SHG (Second Harmonic Generation) effective and high damage threshold. Typically, some non-central structural unit will be introduced to the alkali metal borates or alkaline earth metal borates in order to increase the SHG response, such as, lone-pair metal cations Pb2+, Bi3+. However, there was a contradiction between the SHG effect and bandgap, after the introduction of lone-pair metal cations, the SHG effect will be increased while the bandgap may cause redshift, so exploring the balance between the band gap and SHG effect becomes an urgently solved topic for nonlinear optics research. Based on first-principles calculations, the lone pair containing borates were study on the mechanism. To find the balance between band gap and SHG effect, the influence of lone-pair cation was discussed on two aspects which are redshift of absorption edge and SHG response.(1) In order to exploring the influence of lone-pair cation on the redshift of band gap and the SHG response, BaPb[B5O9(OH)]·H2O, Pb2B5O9Cl, Ba2Pb(B3O6)2, and their isostructual compounds “Ba2[B5O9(OH)]·H2O”, Ba2B5O9Cl and “Ba3(B3O6)2” are studied mainly via DFT calculation. Ba2[B5O9(OH)]·H2O and Ba3(B3O6)2 are virtual structures by simulated calculation. Analyzing the structure and electronic structure of these compounds, the calculated result show that the lead containing borate Pb2B5O9Cl with large redshift, while Ba2Pb(B3O6)2 and BaPb[B5O9(OH)]·H2O with little red-shift, as compared with their isostructural alkaline earth borates. It is found that the ralationship of the redshift of cutoff edge as positive association, and distortion of Pb-O polyhedron agreement with its stereochemical activity. Futhermore, the SHG-density of BaPb[B5O9(OH)]·H2O also be used, it is observed that the lead atom has a contribution to its SHG response.(2) A series of lead borates and its isostructural alkaline earth metal borates are studied to clarify the relationship of the SHG effect and lone pair activity. Through the theoretical simulation calculation, the calculated project density of states and SHG density were achived. The result show that the stronger stereochemical activity of the lead borates are, the more SHG effect gain was.(3) Based on the similarity of lone pair cation model of Bi and Pb, a series of bismuth borates Bi2B8O15, BiB3O6, BiB2O4F and CaBi2B2O7 are studied via DFT calculation. The result show compound Bi2B8O15 has weaker stereochemical activity and with larger band gap and appropriate SHG effect. Meanwhile, the project density of states show that Bi and O paly an impotant role at the Fermi level. The atom-cutting method were used to discuss the original SHG response of these compounds. The researches show that contribution of SHG coefficients mostly from Bi-O group. Through the theoretical simulation calculation, compound Bi2B8O15 was selected out from a series of bismuth borate, and the optical properties of this compound are representation at first time.

文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/4590
专题材料物理与化学研究室
作者单位中国科学院新疆理化技术研究所
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李丹妮. 铅/铋硼酸盐中孤对电子对非线性光学效应及带隙的影响机制研究[D]. 北京. 中国科学院大学,2016.
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