卤素硼酸盐材料的电子结构-性能的DFT研究
发布时间：2019-01-05 19:41
【摘要】：非线性光学晶体是固体激光器进行频率转换的核心器件,受到了科学家们广泛关注。目前为止,亟需探索新的具有优良性能的适用于深紫外波段的非线性光学晶体。有效的设计合成新的非线性光学晶体,需要建立在微观机理的研究基础上。最近通过复合碱金属、碱土金属以及引入卤素,科学家们陆续合成了一大批卤素硼酸盐,但是由于晶体合生长方面等存在困难,依然缺乏应用于深紫外波段的非线性光学材料。本文主要基于密度泛函理论,选择一定体系对卤素硼酸盐的电子结构-光学性质进行研究,讨论了离子替换、活性基元替换对材料光学性质的影响,并寻找出一例具有优良性能的卤素硼酸盐。主要工作如下:(1)基于密度泛函理论,研究了ANa_2B_6O_(13)X(A=Na,Rb;X=Cl,Br)体系中离子替换对带隙和双折射率的影响。电子结构显示这个体系中决定带隙的是B-O键,碱金属离子(Rb+和Na+)和卤素离子(Cl-和Br-)之间的替换对带隙影响不大;碱金属离子之间的替换对双折射率影响较大。Na_3B_6O_(10)X(X=Cl,Br)含有更加共平面化的B_6O_(13)基团,这是它们的双折射率大于RbNa_2B_6O_(13)X(X=Cl,Br)的双折射率的原因。(2)为了寻找具有优良性能非线性光学材料,基于密度泛函理论,我们研究了含有基元B_7O_(13)的卤素硼酸盐MgB_7O_(13)Cl(MBOC)的电子结构和光学性质。计算结果显示化合物MBOC具有大的带隙8.43 eV和可观倍频效应0.41 pm/V,其优良的性能可以和目前为止性能最优异的晶体KBBF(8.64 eV和0.46 pm/V)相媲美。这说明MBOC在短波段有机会得到应用。我们还分析了MBOC具有大带隙和可观倍频效应的原因。采用单轴加压的模拟方法,发现随着外加压强的增大,B_7O_(13)基团的各向异性会增大,MBOC的双折射率也随着增大。本部分工作证实,设计合成含有B_7O_(13)基团的化合物,其中B_7O_(13)基团含有较大畸变的BOx(x=3,4)基团,会获得具有大带隙和可观倍频效应的非线性光学晶体。(3)为了寻找新型非线性光学活性基元,基于密度泛函理论研究了BMO_4(M=P,As)的电子结构及其光学性质。AsO_4基团替换PO_4基团后,BAsO_4依然具有较大的带隙。MO_4(B,P,As)基团和BO_3基团的带隙(?Eg)大小有以下顺序:?Eg(BO_4)?Eg(PO_4)?Eg(AsO_4)≈?Eg(BO_3)。BMO_4(M=P,As)有较大的倍频系数,未成键的O-2p轨道与B/P或As之间的强烈杂化是它们具有较大倍频系数的原因。BAsO_4中四面体基元的各向异性明显大于BPO_4中四面体的基元的各向异性,因此BAsO_4的双折射率较大。本工作表明,AsO_4基团是一种新的非线性光学活性基元,它替换PO_4基团后,不仅保留了大带隙和大倍频之间的平衡,还增大了双折射率。这为设计合成新的应用于深紫外波段的非线性光学材料提供了新思路。
[Abstract]:Nonlinear optical crystal is the core device of solid-state laser frequency conversion, and has been widely concerned by scientists. Up to now, there is an urgent need to explore new nonlinear optical crystals with excellent properties suitable for deep ultraviolet band. The effective design and synthesis of new nonlinear optical crystals need to be based on the study of microscopic mechanism. Recently, a large number of halogen borates have been synthesized by composite alkali metals, alkaline earth metals and the introduction of halogens. However, due to the difficulties in crystal syntheses, there is still a lack of nonlinear optical materials used in deep ultraviolet band. Based on the density functional theory, the electronic structure-optical properties of halogen borates are studied in this paper. The effects of ion substitution and active unit substitution on the optical properties of the materials are discussed. An example of halogen borate with excellent properties was found. The main works are as follows: (1) based on the density functional theory, the effects of ion substitution on the band gap and birefringence in ANa_2B_6O_ (13) X (ANa_2B_6O_) system are studied. The electronic structure shows that the band gap is determined by B-O bond. The substitution of alkali metal ions (Rb and Na) and halogen ions (Cl- and Br-) has little effect on the band gap. The substitution of alkali metal ions has great influence on the birefringence. Na_3B_6O_ (10) X (XnCl _ (13) contains a more coplanar B6O _ (13) group. This is the reason why their birefringence is larger than that of RbNa_2B_6O_ (13) X (XnClCnbr). (2) in order to find nonlinear optical materials with excellent properties, the density functional theory is used. The electronic structure and optical properties of the halogen borate MgB_7O_ (13) Cl (MBOC) containing the basic unit B _ 7O _ (13) have been studied. The results show that the compound MBOC has a large band gap of 8.43 eV and an observable frequency-doubling effect of 0.41 pm/V,. Its excellent performance is comparable to that of the most excellent crystal KBBF (8.64 eV and 0.46 pm/V) so far. This shows that MBOC has an opportunity to be applied in short band. We also analyze the reason why MBOC has large band gap and observable frequency doubling effect. The uniaxial compression simulation method is used. It is found that the anisotropy of B _ S _ 7O _ (13) group increases and the birefringence of MBOC increases with the increase of the applied pressure. In this part, it is proved that the compounds containing B _ S _ 7O _ (13) group have been designed and synthesized, in which the B _ S _ 7O _ (13) group contains a large distorted BOx (XN _ 3O _ (4) group. Nonlinear optical crystals with large band gap and observable frequency doubling effect will be obtained. (3) in order to find new nonlinear optical active elements, the density functional theory (DFT) is used to study BMO_4 (Mupp). The electronic structure and optical properties of As. When the AsO_4 group replaces the PO_4 group, the BAsO_4 still has a large band gap. The band gap (? Eg) of the As) group and the BO_3 group have the following order:? Eg (BO_4)? Eg (PO_4)? Eg (AsO_4) 鈮，
本文编号：2402218
[Abstract]:Nonlinear optical crystal is the core device of solid-state laser frequency conversion, and has been widely concerned by scientists. Up to now, there is an urgent need to explore new nonlinear optical crystals with excellent properties suitable for deep ultraviolet band. The effective design and synthesis of new nonlinear optical crystals need to be based on the study of microscopic mechanism. Recently, a large number of halogen borates have been synthesized by composite alkali metals, alkaline earth metals and the introduction of halogens. However, due to the difficulties in crystal syntheses, there is still a lack of nonlinear optical materials used in deep ultraviolet band. Based on the density functional theory, the electronic structure-optical properties of halogen borates are studied in this paper. The effects of ion substitution and active unit substitution on the optical properties of the materials are discussed. An example of halogen borate with excellent properties was found. The main works are as follows: (1) based on the density functional theory, the effects of ion substitution on the band gap and birefringence in ANa_2B_6O_ (13) X (ANa_2B_6O_) system are studied. The electronic structure shows that the band gap is determined by B-O bond. The substitution of alkali metal ions (Rb and Na) and halogen ions (Cl- and Br-) has little effect on the band gap. The substitution of alkali metal ions has great influence on the birefringence. Na_3B_6O_ (10) X (XnCl _ (13) contains a more coplanar B6O _ (13) group. This is the reason why their birefringence is larger than that of RbNa_2B_6O_ (13) X (XnClCnbr). (2) in order to find nonlinear optical materials with excellent properties, the density functional theory is used. The electronic structure and optical properties of the halogen borate MgB_7O_ (13) Cl (MBOC) containing the basic unit B _ 7O _ (13) have been studied. The results show that the compound MBOC has a large band gap of 8.43 eV and an observable frequency-doubling effect of 0.41 pm/V,. Its excellent performance is comparable to that of the most excellent crystal KBBF (8.64 eV and 0.46 pm/V) so far. This shows that MBOC has an opportunity to be applied in short band. We also analyze the reason why MBOC has large band gap and observable frequency doubling effect. The uniaxial compression simulation method is used. It is found that the anisotropy of B _ S _ 7O _ (13) group increases and the birefringence of MBOC increases with the increase of the applied pressure. In this part, it is proved that the compounds containing B _ S _ 7O _ (13) group have been designed and synthesized, in which the B _ S _ 7O _ (13) group contains a large distorted BOx (XN _ 3O _ (4) group. Nonlinear optical crystals with large band gap and observable frequency doubling effect will be obtained. (3) in order to find new nonlinear optical active elements, the density functional theory (DFT) is used to study BMO_4 (Mupp). The electronic structure and optical properties of As. When the AsO_4 group replaces the PO_4 group, the BAsO_4 still has a large band gap. The band gap (? Eg) of the As) group and the BO_3 group have the following order:? Eg (BO_4)? Eg (PO_4)? Eg (AsO_4) 鈮，
本文编号：2402218
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