共查询到19条相似文献,搜索用时 82 毫秒
1.
采用Hartree-Fock方法和密度泛函 BPW91方法,对TATB分子的几何结构进行了优化,计算了其电子能量和热运动的能量.计算并讨论了TATB的生成焓.结果表明,TATB分子中的苯环离域电子结构引起TATB生成焓计算的较大的系统偏差;利用具有相似离域电子结构的苯和NO的生成焓进行修正,计算得到的TATB生成热与实验结果符合较好.? 相似文献
2.
用分子参数预测烷烃衍生物的标准生成焓 总被引:2,自引:2,他引:0
利用分子参数,即主原子数(N)、主链碳原子数(N')、相对电负性(Xr)、取代参量(P)和官能团位置参量(q)建立了定量预测醇、硫醇、醚、硫醚、醛、酮、酸和酯等烷烃衍生物的标准生成焓数学模型,相关系数均大于0.999,其计算值与相应的文献值都非常吻合,平均相对误差小于1%.分子参数法的物理意义明确、操作简单、使用方便,是进行定量构效相关(OSPR)研究的一种简便可行的方法. 相似文献
3.
结构参数F与部分气态化合物标准生成焓的相关性研究 总被引:9,自引:1,他引:9
用三个分别代表分子中原子联结情况、顶点原子结构特点和相邻原子成键情况的矩阵相乘得到一个无量纲数值的方法定义并计算了拓扑指数F。用F分别相关了16个硅卤化物(不含氢)、32个硅卤化物9含氢)、16个钛卤化物、32个硅卤化物和钛卤化物(不含氢)、48个硅卤化物(含氢)和钛卤化物、44个卤代甲烷的标准生成焓,其相关系数均在0.97以上。F能较好地处理CH4、SiH4等Randic-Kier指数不能处理的 相似文献
4.
秦正龙 《原子与分子物理学报》2004,21(3):532-534
把键参数和量子数引入原子点价,重新定义原子点价为δki,并用δki构建分子结构参数K.K与33种AnXm型过渡元素卤化物的标准生成焓-ΔfHθm呈现高度的相关性,并给出了相关方程,其相关系数为0.991 0.与其它结构参数相比,本参数的计算更为准确.用此模型预测了5个过渡元素卤化物的-ΔfHθm,得到了满意的结果,表明该模型较好地提示了过渡元素卤化物-ΔfHθm的共同规律. 相似文献
5.
三硝基甲烷键离解能和生成焓的理论计算 总被引:5,自引:0,他引:5
采用密度泛函(DFT)四种交换/相关函数(B3LYP、B3P86、B3PW91和PBE0)结合不同的基函数,求得了三硝基甲烷C-NO2键的离解能(BDE),并且通过合理选择参考物硝基甲烷,设计等键等电子对反应,计算了气相三硝基甲烷分子的生成焓(HOF).与实验数据进行比较,PBE0/6-31g*计算出的BDE值最好,误差为-2.1 kcal mol-1;PBE0密度泛函结合带极化函数的6-31g基组得到的HOF值与实验值吻合的最好(误差在0.1 kcal mol-1以内). 相似文献
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7.
合成了一种稀土镨DL α甘氨酸配合物高氯酸盐晶体.经热重、差热及元素的化学分析,确定其组成是[Pr2 (DL αGly)6 (H2O)4 ] (ClO4 )6·5H2O,纯度是99. 63%.熔点分析仪分析知其没有固定熔点. 在79~371K,用高精密全自动绝热量热仪对晶体配合物进行了热容测定,发现该配合物在低温段没有反常热容. 333K附近是该配合物的分解温区,配合物的分解温度、分解焓和分解熵分别是320. 010K、40. 714kJ/mol和127. 227J/molK.计算机拟合了在78. 939~301. 295K热容对温度的多项式方程. 在常压、298. 15K下,用具有恒温环境的反应热量计测定了配合物的标准生成焓值为-8022. 802kJ/mol. 相似文献
8.
采用VUV同步辐射光源,在超声冷却条件了研究四氯化碳,光电离的动力学过程,实验表明,母体离子极不稳定。本文通过对CCl4光解离电解碎片出现势的测定,结果有关确认的势力学数据,了该体系中有关离子的标准生成焓、离子型分子自由基中的键能、中性分子及自由其中的键能和母体离子的解离能等一系列热化学数据。详细探讨了CCl4及VUV光解离电离的通道及其它可能发生的动力学过程。 相似文献
9.
采用热力学方法和Benedict-Webb-Rubin(BWR)方程及相应的参数,计 算了临界温度附近H2气体的绝对焓和熵值,同时拟合了一组高准确度的定压比热容与温度 关联式参数.通过计算值与实验值的比较发现:在临界温度以上,计算值与实验值符合良好 ,对低于临界温度的未饱和H2气体也能计算出较好了结果.但对临界点和温度低于临界温 度、压强高于临界压强的过饱和H2气体的计算误差比较大,说明此时的H2气体的热力学性质特别,应当专门处理. 相似文献
10.
舒远杰 《工程物理研究院科技年报》2009,(1):115-117
1含能材料分子设计理论体系已初步形成从微观结构(电子、分子和晶体结构)出发,综合地运用以量子化学(QC)为核心的当代理论和计算化学方法,包括分子力学、化学动力学等多学科的理论方法,建立了一套系统、有效地评估含能材料多种重要性能的方法。实现了原子化方案及PDDG/MNDO法等3种新的QC半经验方法的计算程序,计算气相摩尔生成热有较高精度。得到计算固态标准生成焓的4种方法,其标准误差均达到了国际先进水平的要求,研究结果见表1。 相似文献
11.
José R. B. Gomes Luísa M. P. F. Amaral Manuel A. V. Ribeiro da Silva 《Journal of Physical Organic Chemistry》2008,21(5):365-371
The standard (p0 = 0.1 MPa) molar enthalpy of formation of 3,4‐dimethylbenzophenone was derived from the standard molar energy of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. The Calvet high temperature vacuum sublimation technique was used to measure the enthalpy of sublimation of the compound. From these experimental parameters, the standard molar enthalpy of formation of 3,4‐dimethylbenzophenone, in the gaseous phase and at T = 298.15 K, was derived as ?(17.1 ± 2.9) kJ mol?1. Density functional theory was used to investigate the gas‐phase molecular energetics of the 12 dimethylbenzophenones. Molecular geometries and vibrational frequencies were computed at the B3LYP/6‐31G(d) level of theory. The larger 6‐311+G(2d,2p) basis set was used to compute the energy of all dimethylbenzophenones and of the other compounds that were considered for the estimation of the standard molar enthalpies of formation at T = 298.15 K. The calculations show that the 2,2′‐ and 4,4′‐dimethylbenzophenones are the least and most stable isomers, respectively. Finally, the calculated enthalpy of formation of the benzophenone that was also studied experimentally, 3,4‐dimethylbenzophenone, is ?16.7 kJ mol?1, which is in excellent agreement with the experimental result. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
12.
室温固相反应制备纳米四水磷酸锌的热化学研究 总被引:3,自引:0,他引:3
以Na3PO4·12H2O和ZnSO4·7H2O为原料,采用室温固相反应制备纳米四水磷酸锌,用微量热法研究该反应的反应焓和四水磷酸锌的标准摩尔生成焓.根据Hess定律,设计了一个新的热化学循环:以4mol/LHCl溶液为量热溶剂,用RD496微热量计于298.15K测定了反应物与产物在量热溶剂中的溶解焓分别为(-47.180±0.084)和(-7.617±0.096)kJ/mol,同时测定两种溶液的紫外光谱、折光率和电导率.两种溶液的紫外吸收曲线重叠,稀释500倍后的电导率值分别是2180、2181μS/cm,折光率值分别是1.3679、1.3678.计算出该固相反应的反应焓为-39.530kJ/mol,同时得到纳米四水磷酸锌的标准摩尔生成焓,推荐其值为-4354.004kJ/mol. 相似文献
13.
A new model different from the Hawking model is suggested to describe the formation of mini (primordial) black holes. It is based on an idea that the fluids, which fill in the universe at the beginning just after the big bang, are separated into mini clusters, moving with supersonic velocities and colliding with each other under the forces of gravitational attractions. We show that between the time era from 10–43 to 10–8 sec. about 36 various generations of mini black holes with masses ranging in the interval 10–5—10–30 gm are possible. 相似文献
14.
本文通过水热法合成了六硼酸钡Ba3B6O9(OH)6,并通过 X射线衍射(XRD)、红外光谱(FT-IR)、综合热分析法(TG-DSC) 和扫描电子显微镜(SEM)对其进行了表征。通过微量热仪测定了Ba3B6O9(OH)6在 0.9995mol·dm-3HCl(aq) 的摩尔溶解焓为(32.34±0.58) kJ·mol-1,并计算了其标准摩尔生成焓为-(7130.664±4.2) kJ·mol-1。此外,通过基团贡献法估算了[B6O9(OH)6]6- 的摩尔生成焓为-5517.744 kJ·mol-1。 相似文献
15.
本文通过分析烷烃核磁共振碳谱(13C NMR)化学位移与生成焓之间的关系,提出由13C NMR化学位移的测定值来确定烷烃生成焓的新方法.用53个烷烃分子的13C NMR化学位移总和(SCS)、三键数(P3)以及碳原子数目(n)与生成焓实验值进行相关,所得回归方程的相关性良好(相关系数R=0.998 2,标准偏差S=3.5 kJ/mol).进而,通过随机抽样和留一法证实该方程具有良好的稳定性和预测能力.将烷烃13C NMR化学位移与其生成焓定量联系起来,不仅有利于深入理解分子结构与性能关系,还为预测那些难于测定且费时的物理化学性质提供了新思路. 相似文献
16.
José R. B. Gomes André R. Monteiro Bruno B. Campos Paula Gomes Maria D. M. C. Ribeiro da Silva 《Journal of Physical Organic Chemistry》2009,22(1):17-23
The present work reports the first experimental thermochemical study of mono‐N‐oxides derived from quinoxaline, namely, 3‐methoxycarbonyl‐2‐methyl‐quinoxaline N‐oxide and 3‐ethoxycarbonyl‐2‐methyl‐quinoxaline N‐oxide. The values of the enthalpies of formation, in the condensed state, and of the enthalpies of sublimation, derived from static bomb calorimetry and Calvet microcalorimetry measurements, respectively, are combined to derive the standard molar enthalpies of formation in the gaseous phase for these two compounds. From the latter values, the first and second N? O bond dissociation enthalpies for the corresponding di‐N‐oxides have been obtained. The gas‐phase experimental results are also compared with calculated data obtained with a density functional theory approach. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
17.
Kinetics and thermochemistry of the gas phase reactions between CH3OCHCl2 (DCDME) and OH radical are investigated theoretically. The geometries and all the stationary points on the potential energy surface are calculated at BHandHLYP/6-311G(d,p) method. The energy information is further refined at CCSD(T)/6-311G(d,p) level of theory. Reaction profiles are modelled including the formation of two pre-reactive and post-complexes. The rate constants, which are evaluated by Canonical Transition State Theory (CTST) including tunnelling correction at 298 K, are in very good agreement with the available experimental data. The percentage contributions of both reaction channels are also reported at 298 K. The hydrogen abstraction reaction from the –CHCl2 group is found to be dominant leading to the formation of CH3OCCl2 + H2O. Using group-balanced isodesmic reactions, the standard enthalpies of formation for CH3OCHCl2, CH3OCCl2 and CH2OCHCl2 are also reported. 相似文献
18.
ZHAO Hui WANG Zhi-Xi 《理论物理通讯》2007,47(1):45-48
We investigate the entanglement of formation for a class of high-dimensional quantum mixed states. We present a kind of generalized concurrence for a class of high-dimensional quantum pure states such that the entanglement of formation is a monotonically increasing convex function of the generallzed concurrence, from the monotonicity and convexity the entanglement of formafion for a class of high-dimensional mixed states has been calculated analytically, 相似文献
19.
Terrestrial laser scanners are geodetic instruments with applications in areas such as architecture, civil engineering or environment. Although it is common to receive the technical specifications of the systems from their manufacturers, there are not any solutions for data verification in the market available for the users. This work proposes a standard artifact and a methodology to perform, in a simple way, the metrology verification of laser scanners.The artifact is manufactured using aluminium and delrin, materials that make the artifact robust and portable. The system consists of a set of five spheres situated at equal distances to one another, and a set of seven cubes of different sizes. A coordinate measuring machine with sub-millimetre precision is used for calibration purposes under controlled environmental conditions. After its calibration, the artifact can be used for the verification of metrology specifications given by manufacturers of laser scanners.The elements of the artifact are destinated to test different metrological characteristics, such as accuracy, precision and resolution. The distance between centres of the spheres is used to obtain the accuracy data, the standard deviation of the top face of the largest cube is used to establish the precision (repeatability) and the error in the measurement of the cubes provides the resolution value in axes X, Y and Z. Methodology for the evaluation is mainly supported by least squares fitting algorithms developed using Matlab programming.The artifact and methodology proposed were tested using a terrestrial laser scanner Riegl LMSZ-390i at three different ranges (10, 30 and 50 m) and four stepwidths (0.002°, 0.005°, 0.010° and 0.020°), both for horizontal and vertical displacements. Results obtained are in agreement with the accuracy and precision data given by the manufacturer, 6 and 4 mm, respectively. On the other hand, important influences between resolution and range and between resolution and stepwidth are observed. For example, the two smaller cubes cannot be well detected in any case and, as must be expected, the increase in range and stepwidth produces a decrease in the quality of the detection for the larger ones. 相似文献