六硝基芪衍生物的红外光谱和热力学性质的理论研究

用量子化学密度泛函理论方法,在B3LYP/6-31G*水平下,对六硝基芪衍生物进行了几何构型全优化和电子结构计算。通过振动分析,求得它们的红外光谱并作归属。将理论计算IR谱与已知实验结果进行比较,表明本文所提供的计算结果是可靠的。对谐振频率以0.96进行标度后基于统计热力学原理求得它们的热力学性质,探讨了热力学性质随硝基数、氨基数、羟基数和温度变化的规律,发现有很好的线性关系,体现了很好的基团加和性。     

三聚氰胺结构和热力学性质的密度泛函理论研究

采用Materials Studio 软件中的DMol~3模块对三聚氰胺的结构和性质进行了理论研究.得到了分子的几何构型、振动频率、各原子上的电荷分布、热力学、以及Fukui指数和前线分子轨道.计算结果表明:三聚氰胺分子中的C原子易得电子,是亲核试剂进攻点,而胺基上的N原子因含孤对电子是亲电反应中心.     

3C-SiC的结构和热力学性质

利用第一性原理平面波模守恒赝势密度泛函理论研究了3C-SiC的结构, 其零温(0 K)零压下的晶格常数、体弹模量及其对压强的一阶导数、弹性常数的计算结果与实验值和其它理论计算结果相符合. 通过准谐德拜模型, 得到了不同温度不同压强下的热容和德拜温度, 发现热容随着压强增加而减小, 德拜温度随压强增加而增加, 并成功地获得了相对晶格常数、相对体积、体弹模量、热膨胀系数与温度和压强的关系.     

苯和苯胺类硝基衍生物的红外光谱和热力学性质的理论研究

用量子化学密度泛函理论方法,在B3LYP/6-31G*水平下,对苯和苯胺类硝基衍生物进行了几何构型全优化和电子结构计算。通过振动分析,求得它们的红外光谱并作归属。将理论计算IR谱与已知实验结果进行比较,表明本文所提供的计算结果是可靠的。对谐振频率以0.96进行标度后基于统计热力学原理求得它们的热力学性质,探讨了热力学性质随硝基数、氨基数和温度变化的规律,发现有很好的线性关系,体现了很好的基团加和性。     

PdH_2和YH_2分子热力学稳定性的理论研究

由于纯钯的渗氢速率较低,关于钯合金渗氢材料[1-3]的研究引起广泛关注,如钯钇合金.已有研究报道[3,4]PdH2和YH2分子可能的电子结构、势能函数与光谱性质,并提供了可靠的研究方法.     

多溴二苯并呋喃的热力学性质和稳定性的密度泛函理论研究

在B3LYP/6-31G*水平上对二苯并呋喃和135个多溴二苯并呋喃系列化合物(PBDF)进行了全优化计算和振动分析, 得到各分子的总能量(E_T)、焓(H⁰)、熵(S⁰)、自由能(G⁰)和恒容热容(C_V⁰), 研究了这些参数与溴原子的取代数目及取代位置的关系. 溴原子置换在不同位置时, 使E_T, H⁰和G⁰数值增加大小次序为: 1(9)＞3(7)＞2(8)＞4(6), 即置换在1(9)位最不稳定; 两个溴原子处在同一苯环时, E_T, H⁰和G⁰数值也都增加, 增加的顺序为: 邻>>间＞对, 即相互处于邻位最不稳定. 而且有两个溴原子同时取代在1和9位时, 使H⁰和G⁰的数值的增加比取代在邻位、间位和对位时的增加值都大. 每增加1个溴原子, S⁰增大约40.1 J•mol^－1•K^－1, C_V⁰增大约16.3 J•mol^－1•K^－1. 同时, 设计等键反应, 计算了各异构体的标准生成热(H_f⁰)和标准生成自由能(G_f⁰). 根据异构体自由能的相对大小, 从理论上求得异构体的相对稳定性顺序, 各异构体组中的稳定性顺序与PCDF系列的稳定性顺序基本一致.     

氟、氯和甲基取代丁二酰亚胺的结构、红外光谱和热力学性质的密度泛函理论研

用密度泛函理论（DFT）的B3LYP方法（6－31G基组）,计算研究了丁二酰亚胺（SIM）的氟、氯和甲基取代物（SIMF,SIMCI和SIMMe)的几何构型、电子结构、红外光谱和热力学性质,讨论了取代基效应。结果表明,SIMF和SIMCI均为平面构型,SIMMe接近平面构型。羰基伸缩振动频率（vc=o)均分裂为两个谱带,低频带出现在1734-1771cm^-1,高频带出现在1792－1822cm^-1,且前者强于后者。与SIM相比,吸电子基（F和CI）使vc=0和偶极矩增大,推电子基（CH3）的影响正相反。由校正频率计算了298－800K温度范围的热力学性质熵（S°）和热容（Cp°）。     

戊唑醇的分子结构、理论计算及热力学性质研究

在甲苯溶剂中利用缓慢蒸发法得到1-(4-氯苯基)-4,4-二甲基-3-(1H-1,2,4-三唑基甲基)戊醇-3（戊唑醇）的单晶,通过 X射线单晶结构分析法测定其晶体结构,晶体属单斜晶系,空间群为P2(1)/c,晶胞参数为：a = 1.1645(1) nm,b = 1.6768(2) nm,c = 1.7478(2) nm,β= 92.055(2),Dcalc.= 1.199 g/cm3,Z = 4,F(000)= 264。运用密度泛函理论 (DFT) B3LYP得到其优化几何构型并得到其频率。计算得到的结构参数与相应的实验值十分接近。运用微热量仪对标题物进行比热容测定,在所测温度范围283~353 K内,比热容随温度呈稳定的线性变化,根据测定的比热容方程,计算出戊唑醇以298.15 K为基础在283~353 K温区的的热力学函数：焓、熵和吉布斯自由能。     

用密度泛函理论研究多氯代菲醌的结构和热力学性质

使用Gaussian 03程序,采用密度泛函理论(DFT)在B3LYP/6-31G*水平上对136个多氯代9,10-菲醌(PCPQ)系列化合物进行全优化和振动分析,得到各分子在298.15K、101.3kPa状态下的优势构型.结合Gaussian 03程序的输出文件,计算了PCPQ化合物在200K至1 000K的摩尔恒压热容(Cp,m).用SPSS13.0对Cp,m与温度进行多元线性回归.结果表明:氯原子取代模式对PCPQ化合物的扭角A(C4-C9-C10-C5)有很大的影响;与此同时,Cp,m与T,T-1和T-2之间有着很好的相关性(r2=1.00).     

二芴及其衍生物的结构优化、前线轨道及其性质的理论研究

采用DFT/B3LYP方法对系列二芴体系进行了全优化, 对其结构特征进行对比. 在此基础上, 得到各分子的最高占据轨道和最低空轨道能量关系及HOMO-LUMO能隙, 并分析其能隙与导电性的关系及预计其光谱特征. 对各分子的相关热力学性质进行了研究. 热力学参数表明各分子均较稳定, 其中化合物DFBT最稳定. 采用ZINDO和TD-DFT方法计算其吸收光谱, 分析结构特征对光谱性质的影响. 二芴中插入共轭程度高的结构后, 分子的共轭程度增加; HOMO-LUMO能隙变窄; 最低激发能降低, 导电性增强; 吸收光谱红移. 而接入扭曲的结构后, 共轭程度降低; HOMO-LUMO能隙变宽; 最低激发能有所升高, 导电性下降; 吸收光谱蓝移.     

Theoretical investigations on structure,density, detonation properties,and sensitivity of the derivatives of PYX

The ? NH₂, ? NO₂, ? N₃, ? NHNO₂, and ? ONO₂ substitution derivatives of PYX (2,6‐bis(picrylamino)‐3,5‐dinitropyridine) were studied at the B3LYP/6‐31G** level of density functional theory. The sublimation enthalpies and heats of formation (HOFs) in gas phase and solid state of these compounds were calculated. The theoretical predicted density (ρ), detonation pressure (P), and detonation velocity (D) showed that these derivatives have better detonation performance than PYX. The effects of substituent groups on HOF, ρ, P, and D were discussed. The order of contribution of various groups to P and D was ? ONO₂ > ? NO₂ > ? NHNO₂ > ? N₃ > ? NH₂. Sensitivity was evaluated using the frontier orbital energies, bond orders, bond dissociation enthalpies (BDEs), and characteristic heights (h₅₀). The trigger bonds in the pyrolysis process for these PYX derivatives may be Ring‐NO₂, NH? NO₂, or O? NO₂ varying with the substituents. The h₅₀ of most compounds are larger than that of CL‐20, and those of ? NH₂, ? NO₂, and most ? ONO₂ derivatives are larger than that of RDX. The BDEs of the trigger bonds of all but the ? ONO₂ derivatives are sufficiently large. Taking both detonation performance and sensitivity into consideration, some derivatives of PYX may be good candidates of explosives. © 2012 Wiley Periodicals, Inc.     

Theoretical prediction of the electronic and thermodynamic properties of YN‐ZrN solid solutions

In this study, the results of structural parameters, electronic structure, and thermodynamic properties of the Zr_xY_1–xN solid solutions are presented. The effect of zirconium composition on lattice constant, and bulk modulus shows nonlinear dependence on concentration. Deviations of the lattice constant from Vegard's law and deviations of the bulk modulus from linear concentration dependence were found. Our findings indicate that the Zr_xY_1–xN solid solutions are metallic for x = 0.25, 0.5, 0.75. The calculated excess mixing enthalpy is positive over the entire zirconium composition range. The positive mixing enthalpies for Zr_xY_1–xN alloys indicate the existence of miscibility gaps and spinodal decompositions. The effect of temperature on the volume, bulk modulus, Debye temperature, and the heat capacity for Zr_xY_1–xN alloys were analyzed using the quasi‐harmonic Debye model. Results show that the heat capacity is slightly sensitive to composition as temperature increases. © 2015 Wiley Periodicals, Inc.     

Electronic structure and spectroscopic properties of 6‐aminophenanthridine and its derivatives: Insights from density functional theory

6‐Aminophenanthridine (6AP) and its derivatives show important biological activities as antiprion compounds and inhibitors of the protein folding activity of the ribosome. Both of these activities depend on the RNA binding property of these compounds, which has been recently characterized by fluorescence spectroscopy. Hence, fundamental insights into the photophysical properties of 6AP compounds are highly important to understand their biological activities. In this work, we have calculated electronic structures and optical properties of 6AP and its three derivatives 6AP8CF₃, 6AP8Cl, and 6APi by density functional theory (DFT) and time‐dependent density functional theory (TDDFT). Our calculated spectra show a good agreement with the experimental absorption and fluorescence spectra, and thus, provide deep insights into the optical properties of the compounds. Furthermore, comparing the results obtained with four different hybrid functionals, we demonstrate that the accuracy of the functionals varies in the order B3LYP > PBE0 > M062X > M06HF. © 2015 Wiley Periodicals, Inc.     

全氟化合物热力学性质的密度泛函理论研究

用密度泛函理论B3LYP方法,在6-31G基组水平上,对12个全氟化合物分子进行了全优化计算,得到其分子零点振动能EZPV、热能校正值Eth、恒容热容CVΦ、标准熵SΦ以及配分函数lgQ等热力学参数,并计算了这些分子的电性拓扑状态指数Em.通过最佳变量子集回归建立了电性拓扑状态指数与热力学参数之间的QSPR模型,模型的相关系数R2分别为1.000,1.000,1.000,0.999和1.000,采用逐一剔除法得到的交叉验证相关系数R2cv分别为0.999,1.000,1.000,0.999和1.000,利用建构的数学模型得到热力学性质的相对平均误差分别为0.43%,0.41%,0.46%,0.41%和0.71%.从方程可以看出,F原子取代基数量是影响全氟化合物分子热力学参数大小的主要因素,检验证明所建模型具有良好的稳定性和预测能力.     

Mechanistic insights on how hydroquinone disarms OH and OOH radicals

Phenol derivatives are distinguished as successful free radical scavengers. We present a detailed analysis of hydroxyl hydrogen abstraction from hydroquinone by hydroxyl and hydroperoxyl radical with emphasis on changes that take place in the vicinity of the transition state. Quantum theory of atoms in molecules is employed to elucidate the sequence of positive and negative charge transfer by studying selected properties of the three key atoms (the transferring hydrogen, the donor atom, and the acceptor atom) along intrinsic reaction path. The presented results imply that in both reactions, which are examples of proton coupled electron transfer, proton, and electron get simultaneously transferred to the radical oxygen atom. The fact that the hydrogen's charge and volume do not monotonously change in the vicinity of the transition state in the product valley results from the adjacency of the proton and the electron to the donor and the acceptor oxygen atoms. Obtaining a detailed understanding of mechanisms by which free radicals are disarmed is of paramount importance given the effects of those highly reactive species on biological systems. A comprehensive analysis of hydroxyl hydrogen abstraction from hydroquinone by hydroxyl and hydroperoxyl radicals, based on changes of selected electronic properties of the three most relevant atoms (hydrogen donor, hydrogen acceptor, and the hydrogen itself), along the reaction coordinate, can be obtained by first‐principles calculations.     

特丁基对苯二酚对生物柴油的抗氧化性能研究

生物柴油的氧化安定性是确保生物柴油品质的关键因素。本文采用欧盟标准(EN14214-2002),使用瑞士万通公司生产的873型生物柴油氧化安定性测定仪,采用在植物油抗氧化方面最常用、最有效的特丁基对苯二酚(TBHQ)对由地沟油、大豆油和棉籽油制成的生物柴油的抗氧化性进行了系统的定量研究。结果表明,当添加量大于0.6‰时,3种生物柴油抗氧化时间均超过国标规定的6h。TBHQ是一种理想的生物柴油抗氧化剂,对比另一种常用的抗氧化剂BHA(叔丁基对羟基茴香醚)抗氧化性能优势明显。     

Theoretical study on tetrazole and its derivatives (3) MP2 and thermodynamic calculations of amino derivatives of tetrazole

Fully optimized geometries and electronic structures of amino derivatives of tetrazole are obtained at MP2/6-31G* level. The tetrazole rings are planar and aromatic for all the amino derivatives of tetrazole. The amino group is not co-planar with the ring and its conformation is mainly determined by the lone pair electronic repulsion between the substituent and the ring. N(4) atom is more negatively charged and is the most probable coordination site. The energy gaps between LUMOs and HOMOs of 2H-aminotetrazoles and C-aminotetrazole neutrals are smaller than those of the corresponding 1H-isomers and N-aminotetrazole neutrals respectively. The IR frequencies, thermodynamic properties and temperature-dependent functions for heat capacities in the form (a bT cT2) in the 300-1000K range are reported.     

Theoretical study of the structures and properties of cyclic nitramines: Tetranitrotetraazadecalin (TNAD) and its isomers

Density Functional Theory (DFT) was employed to study the geometries, electronic structures, infrared vibrational spectra, and thermodynamic properties of seven isomeric cyclic nitramines of C₆H₁₀N₈O₈ (i.e., TNAD and its six isomers) at the B3LYP/6‐31G* level of theory. The experimental results available for TNAD were used to determine the reliability of the DFT method for generating structural and IR spectroscopic values for these molecular systems. The relative stabilities of the conformers were evaluated from the energy differences of the structures. Detonation properties of various conformers were evaluated using the Kamlet‐Jacobs equations, and it was found that all the calculated results are comparable to the available experimental data. In addition, the calculated results demonstrate that all title compounds can be used as excellent propellant ingredients. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005