钠钛硅酸盐精细结构及其拉曼活性分子振动的量子化学从头计算研究

本文选取了Na_2O-TiO_2-SiO_2体系不同成分的团簇模型,采用量子化学从头计算方法计算其拉曼振动频率和相对散射活性。本文分析了钛硅酸盐中硅氧四面体([SiO_4])的局域环境变化对特征拉曼振动频率的影响,对硅氧四面体应力指数进行了拓展与修正,研究表明钠钛硅酸盐拉曼光谱高波数区硅氧四面体非桥氧对称伸缩振动频率随相应的硅氧四面体应力指数的增加而增加,并表现出良好的线性相关性。采用拉曼光谱和~(29)Si NMR对Na_2TiSiO_5玻璃进行解谱、定量分析和比较,并认为869 cm~(-1)处的谱峰归属为Q_(1(Si))中非桥氧的对称伸缩振动。     

链状硅酸盐矿物的拉曼光谱研究

本文基于密度泛函理论(DFT)的平面波赝势法,利用CASTEP计算模块对四种典型链状(铝)硅酸盐矿物进行拉曼振动活性与拉曼光谱的模拟计算,同时测定了矿物的拉曼光谱,确定了四种矿物拉曼振动谱峰的归属,并结合硅氧四面体应力指数(SIT)进行了分析。结果表明,CASTEP计算模块可以有效获知(铝)硅酸盐矿物特征结构的拉曼振动模式的归属;链状(铝)硅酸盐矿物硅氧四面体局域环境与SiOT非桥氧对称伸缩振动波数之间的关系仍可用SIT指数描述。     

NaF-AlF3二元系铝氟四面体团簇结构的拉曼光谱表征与量子化学从头计算

本文构建了一系列NaF-AlF3二元系铝氟四面体团簇结构模型, 应用量子化学从头计算方法, 采用Restricted Hatree-Fock(RHF)自洽场方法和6-31G(d)基组对结构进行优化, 并用相同的方法和基组进行分子振动模式的模拟计算。考虑相邻铝氟四面体的影响, 引入四面体应力指数(SIT)的概念分析和讨论该二元系高频区非桥氟对称伸缩振动及中频区桥氟对称弯曲振动模式。研究表明, 高频区铝氟四面体非桥氟对称伸缩振动频率与其铝氟四面体的种类(Qi)密切相关, 且铝氟四面体非桥氟对称伸缩振动频率的值随SIT值的增大而增大, 呈现较好的线性关系。同时, NaF-AlF3二元系团簇结构的中频区桥氟对称弯曲振动频率主要受桥氟角度的影响。并采用高温拉曼仪测定了分子比为NaF:AlF3 =1∶2体系的升温拉曼光谱, 随着温度的升高NaF:AlF3 =1∶2体系的主峰逐渐向低频移动, 观察到Q0、Q1、Q2峰位的变化。     

二元碱金属硅酸盐精细结构和拉曼光谱的从头计算研究

应用量子化学从头计算方法研究了二元碱金属硅酸盐的精细结构,对典型的系列二元碱金属硅酸盐离子簇模型采用6-31G(d)基组和闭壳层Hartree-Fock(RHF)方法优化构型,并计算了二元碱金属硅酸盐的拉曼光谱,采用硅氧四面体应力指数这一精细结构参数分析和讨论了计算得到的非桥氧高频区对称伸缩振动频率和其拉曼光学活性,以及不同阳离子对该拉曼光学活性的影响。研究表明,二元碱金属硅酸盐非桥氧高频区对称伸缩振动频率与其精细结构密切相关,而且与Q₃相连的Q₄会对该Q₃的拉曼光学活性表现出增强作用。这说明二元碱金属硅酸盐的拉曼散射等性质主要依赖于其精细结构而非其初级结构单元-硅氧四面体。研究还表明,半径较大的阳离子有利于增强离子簇的拉曼光学活性,但对于小的离子簇,过多的电荷迁移反而会起到抑制作用。     

Na_2O-Al_2O_3二元系团簇微结构与特征拉曼振动波数的相关性

针对含铝四配位Na_2O-Al_2O_3二元系熔体团簇结构,构建了九种团簇模型,并对其拉曼振动波数和散射活性进行了密度泛函理论(DFT)计算。微结构的命名参考了硅酸盐体系的命名规则~([1]),其中Al-O四面体简记为Qi(i为桥氧数)。分析表明,Na_2O-Al_2O_3二元系团簇中Q_2和Q_3微结构单元中Al-O_(nb)(non-bridging oxygen,即非桥氧)键对称伸缩振动波数随其键长呈现线性相关性。Q_2和Q_3微结构中铝氧键长随着参与成环铝氧四面体的数目的增加而增加,这些相关性有助于Na_2O-Al_2O_3二元系熔体中铝氧四面体连接方式及团簇的诊断和鉴别。     

CaO-Al2O3-SiO2熔渣结构和热导率的分子动力学模拟

利用分子动力学模拟研究CaO-Al₂O₃-SiO₂三元熔渣的微观结构和热导率。针对六组不同Al₂O₃含量的熔渣,基于BMH势函数分析了径向分布函数、键长、键角分布函数、氧类型和微结构单元Qⁿ等微观结构信息。结果表明硅和铝在熔渣中以四面体网络结构存在,硅氧四面体较铝氧四面体更为稳定。随着铝含量增加,熔体中的键长和四面体中心角无明显变化,Al-O-Al和Si-O-Al键角逐渐减小;网络中的桥氧(BO)和三配位氧(TO)含量增加,Q³和Q⁴含量增多,在高铝区出现较多的五配位铝(Al^V)。采用Muller-Plathe方法计算了熔渣的热导率,随着铝替代硅原子,网络的聚合程度增加,强化了熔体的热输运能力,热导率呈现增大趋势。     

铝硅酸盐Raman活性分子振动解析

分别测定了蓝晶石、红柱石和硅线石三种铝硅酸盐天然矿物晶体以及K₂O-Al₂O₃-SiO₂三元铝硅酸盐玻璃的Raman光谱。构建了一组硅铝四面体聚集体结构模型,采用量子化学自洽场分子轨道从头计算的方法计算了其Raman振动频率。分析研究了上述Raman光谱振动特征,确定了特征谱峰的归属,解析了铝对铝硅酸盐Raman活性分子振动特征的影响。结果表明,随四配位铝的增加,导致800～1 200 cm-1波数区间内谱峰频率降低,该区间的谱峰是Si—O_nb间非桥氧对称伸缩振动引起的,其中不含Al—O振动;700～800 cm-1区间内出现的谱峰归属于Al—O_nb间非桥氧的对称伸缩振动。     

xCaSiO3·LiBO2固溶体中硅氧四面体微结构形态的拉曼光谱研究

本文测定了xCaSiO3*LiBO2(重量比,x=0, 0.25, 0.33, 0.50)系列的拉曼光谱,分析了硅氧四面体的微结构形态及其随SiO2 浓度的变化.结果表明,在所研究的浓度范围内,其微结构单元,即Qi ( i = 0～4) 均以孤立的硅氧四面体存在,且随SiO2 浓度的增加, Q2, Q4 的丰度有明显增加;此外,硅氧四面体的伸缩振动谱峰的积分强度总和与SiO2 浓度呈线性相关,为采用拉曼光谱直接分析矿物、炉渣、玻璃和土壤中的SiO2 提供了可能.     

硅酸盐熔体微结构单元的对称伸缩模的拉曼散射系数

通过一种新开发的模拟计算方法，计算了硅酸钠熔体的拉曼谱，及其在高频区代表5种硅氧 四面体(用Qi表示，其中i表示桥氧数)的特征峰的拉曼散射系数Si，发现成分的变化对5 种Qi的特征峰的拉曼散射系数的影响非常小.在此基础上取平均分别得到：S0=1,S1=0 ．514,S2=0242,S3=0090和S4=0015然后将计算得到的散射系数应用于二硅酸 钠熔体的实验谱图的定量分析中，得到了该熔体中硅氧四面体单元的分布.同时从计算与试 验谱图的定量解谱中发现，钠系硅酸盐熔体谱中Q0和Q2的ASS模所产生的散射信号 不容忽视. 关键词： 拉曼散射系数 硅氧四面体 硅酸盐熔体 高温拉曼谱     

稀土五磷酸盐晶体的晶格振动

在80K及室温下测量了单斜I LnP_5O_(14)(La～Tb)的偏振拉曼光谱,并分析了谱线的归属。测量结果及群论分析表明。(PO_4)~(3-)四面体的振动频率对晶体结构很敏感,镧系收缩引起的频移与振动性质以及镧氧配位体、磷氧四面体的结构方式有关。     

Features of atomic and electronic structure of oxides on porous silicon surface according to XANES data

Based on synchrotron research of the fine structure main parameters of SiL _{2, 3} X-ray absorption edges (X-ray absorption near edge structure (XANES)) in porous silicon on boron-doped Si(100) wafers, the thickness of the surface oxide layer and the degree of distortions of the silicon-oxygen tetrahedron in this layer were estimated. The thickness of the oxide layer formed on the amorphous layer coating nanocrystals of porous silicon exceeds the thickness of the native oxide on the surface of Si(100) : P and Si(100) : B single-crystal (100) silicon wafers by several times. Distortion of the silicon-oxygen tetrahedron, i.e., the basic unit of silicon oxide, is accompanied by Si-O bond stretching and an increase in the angle between Si-O-Si bonds.     

NIR‐FT Raman and FT‐IR spectral investigations of the nonlinear optical chromophore p‐bromoacetanilide

Vibrational spectral analysis of the hydrogen‐bonded nonlinear optical (NLO) material p‐bromo acetanilide (PBA) was carried out using NIR‐FT‐Raman and FT‐IR spectroscopy. Ab initio molecular orbital computations were performed at HF/6‐31G (d) level to derive equilibrium geometry, vibrational wavenumbers, intensities and first hyperpolarizability. The lowering of the imino stretching wavenumbers suggests the existence of strong intermolecular N H···O hydrogen bonding, which was substantiated by the natural bond orbital (NBO) analysis. The vibrational spectra confirm that the charge‐transfer interaction between the  NHCOCH₃ group and—Br through phenyl ring is responsible for simultaneous strong IR and Raman activation of the ring mode 8a. Vibrational analysis indicates that the lowering of stretching wavenumbers of methyl group due to electronic effects simultaneously caused by induction and hyperconjugation is due to the presence of the oxygen atom. The presence of blue‐shifting H‐bonds of CH stretching wavenumbers, simultaneous activation of carbonyl stretching mode, the strong activity of low‐wavenumber H‐bond stretching vibrations and the role of intramolecular charge transfer in making the molecule NLO active have been analyzed on the basis of the vibrational spectral features. Copyright © 2007 John Wiley & Sons, Ltd.     

阳离子对硅酸盐玻璃激光拉曼光谱影响的研究

运用拉曼光谱技术研究了Na2O(K2O)—CaO(MgO)—SiO2,Na2O(K2O)—Al2O3—SiO2,Na2O(K2O)—B2O3—SiO2,Na2O(K2O)—PbO—SiO2和PbO—BaO—SiO2五个系统的玻璃。结果表明,阳离子对玻璃近程结构的改造会引起拉曼特征的变化。部分样品是根据古玻璃平均成分在实验室烧制的,这项研究对于运用激光拉曼光谱区分不同系统的古代硅酸盐玻璃有重要意义。     

Structural and nonlinear optical properties of cross‐conjugated system benzophenone thiosemicarbazone: a vibrational spectroscopic study

The nonlinear optical (NLO) compound of interest benzophenone thiosemicarbazone (BTSC) was grown and the molecular structure generated with the aid of density functional theory (DFT). FT‐Raman and IR spectra were recorded and analyzed. The harmonic wavenumbers and IR and Raman intensities were computed with the B3LYP method. The observed vibrational wavenumbers were compared with the calculated results. The assignments of the experimental spectra were made with the help of normal coordinate analysis (NCA) following the scaled quantum mechanical force field (SQMFF) methodology. The electronic structure of the most important molecular fragments is described in terms of natural bond orbital (NBO) analysis. Copyright © 2010 John Wiley & Sons, Ltd.     

HNO二聚体蓝移氢键的理论研究

利用分子轨道从头算理论和密度泛函理论结合不同理论基组对于N-H…O蓝移氢键进行了详细的研究.利用标准方法和均衡校正方法对二聚体进行了几何优化,振动频率和相互作用能的计算.拓扑学和自然键轨道理论对于蓝移氢键的本质进行分析.自然键轨道(NBO)分析表明,σ*(N-H)轨道上电子密度降低是电子密度重排效应的结果.分子内电子重排、轨道再杂化和电子受体内部结构重组共同作用结果导致了N-H的振动频率大幅蓝移现象的出现.     

Coadsorption of trimethyl phosphine and thiocyanate on colloidal silver: a SERS study combined with theoretical calculations

The adsorption of trimethyl phosphine (TMP) on colloidal silver has been investigated by means of surface‐enhanced Raman scattering spectroscopy (SERS). On the basis of surface selection rules, it is deduced from the SERS results that TMP adsorbs on silver surface via its P atom. The electron donor effect of TMP can be sensitively probed by the coadsorbed SCN⁻. The Raman wavenumber of νCN of the adsorbed SCN⁻ shifts to lower wavenumbers when TMP is coadsorbed with SCN⁻ and the red shift of C≡N stretching wavenumber is found to increase with increasing surface coverage of TMP. This could be explained in terms of the electron donor effect of TMP. Density functional theory (DFT) calculations further confirm the experimental results that the charge transfer is from TMP to silver surface rather than reversely. Natural bond orbital (NBO) analysis indicates that the red shift of C≡N stretching mode is due the increase of electronic populations of π* orbital of C≡N bond induced by coadsorbed TMP, consequently the C≡N bond is weakened, and the νCN shifts to lower wavenumbers. An NBO analysis also indicates that the conjugated effect between S atom and C≡N bond could easily make the charge transfer from silver surface to C≡N bond. Copyright © 2008 John Wiley & Sons, Ltd.     

Vibrational spectra and structural studies of nonlinear optical crystal ammonium D,L‐tartrate: a density functional theoretical approach

Single crystals of ammonium D , L ‐tartrate, a potential nonlinear optical (NLO) material of interest, were grown by the slow evaporation technique. The crystal structure was determined by single‐crystal X‐ray diffraction. Fourier transform infrared and Raman spectra of the crystallized molecule were recorded and analyzed. The geometry, intermolecular hydrogen bonding, first hyperpolarizability and harmonic vibrational wavenumbers were calculated with the help of B3LYP density functional theory method. The red shift of hydroxyl and NH₄⁺ stretching wavenumbers indicate the formation of inter‐ and intramolecular hydrogen bonding. Simultaneous activation of CH stretching wavenumbers shows the presence of intramolecular charge transfer in the molecule. Natural bond orbital analysis was carried out to demonstrate the various inter‐ and intramolecular interactions that are responsible for the stabilization of this molecule, leading to high NLO activity. Copyright © 2010 John Wiley & Sons, Ltd.