锆钴合金氢化反应热力学函数的计算

在有效原子实势近似下,采用Gaussian 98计算程序及B3LYP/SDD密度泛函方法计算得到了ZrCo和ZrCoH分子的结构、力常数、离解能,能量(E)、熵(S)以及ZrCo与氢同位素气体反应的热力学函数.在固态ZrCo、ZrCoH(D、T)的E和S的计算中,近似以气态分子总能量中的振动能EV代替该分子处于固态时的振动能量,以电子运动和振动运动熵SEv代替分子处于固态的熵,在这种近似下,计算了不同温度下ZrCo与H2、D2、T2反应的ΔH、ΔG、ΔS及氢化反应平衡压力,导出了氢化反应温度与平衡压力的依赖关系.计算得出：ZrCoH、ZrCoD、ZrCoT的生成焓(398～598 K）分别为82.81、81.54和80.49 kJ•mol－1,与实验结果有很好的一致性,表明这种近似处理方法是合理的,可以用于一些未知氢化物的热力学函数的近似计算.     

N2在Pd金属表面的吸附行为

对Pd原子采用相对论有效原子实势(RECP/SDD), N原子采用AUG-cc-pVTZ基函数, 利用B3LYP方法计算了PdN和PdN2分子的微观结构以及不同温度下的热力学函数. 以气态分子总能量中的振动能EV代替该分子处于固态时的振动能量, 以电子运动和振动运动熵SEV代替分子处于固态的熵的近似方法, 计算了不同温度下金属Pd与N2反应的ΔHӨ、ΔSӨ、ΔGӨ及氮化反应平衡压力, 导出了氮化反应平衡压力与温度的关系. 由此可看出, 在常压及298.15～998.15 K温度条件下, N2在金属Pd表面的吸附过程以Pd(s) + N2 = PdN2(s)反应进行. 计算得出在标准条件下, PdN(s)的生成焓为254.37 kJ·mol-1, PdN2(s)的生成焓为－80.59 kJ·mol-1. 并与Pd氢化反应平衡压力比较, 得到平衡常数Kp(N2)比Kp(H2)约小两个数量级, 说明N2较难被金属Pd表面吸附, 在热力学上有利于氢置换氮.     

UO2、UC2和UCO分子的结构和热力学性质

用密度泛函B3LYP方法,计算了UO2、UC2和UCO分子的结构和热力学函数,计算了固体U的振动内能Ev、振动和电子熵Sev,以及U在不同气氛（O2、C2、CO）中形成UO2、UC2和UCO晶体的ΔHfΘ、ΔSfΘ和ΔGfΘ.结果表明,UO2晶体最稳定.     

有镁热反应吗——由一道高考化学题引起的思考

通过近似计算2Al＋Fe2O3=2Fe＋Al2O3,3Mg＋B2O3=2B＋3MgO,Na＋KCl=K↑＋NaCl等金属热还原反应在298 K时的标准摩尔吉布斯自由能变ΔrGøm、标准摩尔反应热ΔrHøm及标准摩尔熵变ΔrSøm,判断这些反应能否进行及焓变、熵变对反应的贡献。     

L-苏糖酸镁的制备及标准生成焓

以L-苏糖酸钙与草酸的复分解反应得到的L-苏糖酸溶液，在80 ℃下与过量MgO反应较长时间， 滤液浓缩后加无水乙醇制得L-苏糖酸镁白色粉末.用化学分析及元素分析确定其组成为Mg(C4H7O5)2•H2O. IR光谱分析表明,化合物中苏糖酸以羧基氧原子与Mg2＋配位，Mg2＋为sp3杂化态，配位数为4. TD－DTG结果说明，它在热分解中有一定稳定性，而经脱水和生成Mg(OAc)2，最后生成MgO.用转动弹热量计测得其恒容燃烧能ΔE为 (－10407.34±4.67) kJ•mol－1,计算其标准燃烧焓ΔcHm和标准生成焓ΔfHm分别为(－3 249.49±1.46) kJ•mol－1和(－2 786.23±1.84) kJ•mol－1.     

稀土气态配合物GdAl3Br12的热力学研究

通过骤冷法实验, 在622～770 K的温度范围和0.0075～0.18 Mpa的压力范围内, 对气态配合物GdAlxBr3x 3的形成热力学进行了探讨. 结果显示, 溴化钆与气态溴化铝二聚体生成唯一产物GdAl3Br12气态配合物; 反应GdBr3(s) (1/2) Al2Br6(g)=GdAl3Br12 (g)的平衡常数、焓变和熵变, 通过骤冷法实验和计算得出.     

用均根拓扑指数与路径数预测链烷烃的沸点和热力学性质

以距离矩阵为基础，建构调和均根拓扑指数（K），以表征链烷烃分子的大小 和分支情况，85种链烷烃的沸点(T_b)、标准生成焓(Δ_rH_m~θ)、标准熵(S_m~θ )、标准生成自由能(Δ_fG_m~θ)与K及路径数(P_2, P_3)的回归方程为: ln(793- T_b) = 6.48346-0.10092K + 0.00131P_2-0.01110P_3, R = 0.9996; -Δ_fH_m~θ = 62.664 + 25.331 K + 6.597 P_2 - 0.678 P_3, R = 0.9984; S_m~θ = 170. 691 + 67.425 K - 4.712P_2 + 5.251 P_3, R = 0.9989; Δ_fG_m~θ = -45.677 + 10.060 K + 0.555 P_2 + 2.342P_3, R = 0.9935。它们的计算值与相应实验值 都非常吻合。结果表明，K对链烷烃具有良好的结构选择性和性质相关性。     

RbCl由H2O至混合溶剂(H2O-DMF)标准迁移熵的测定

电解质迁移热力学性质的测定,对于离子溶剂化的研究具有重要意义.迁移自由能主要反映离子与溶剂分子间的相互作用,迁移熵则主要反映不同溶剂分子间的相互作用,迁移熵随温度及溶剂组成的改变可为溶剂的原有结构推测及溶液秩序改变提供信息.我们曾运用离子选择性电极测定了部分碱金属卤化物在水及含水混合溶剂中的热力学性质[1-3].本文用离子选择性电极方法,通过测定不同温度下电池的标准电动势,根据溶液热力学原理,求得ＲｂＣｌ由Ｈ2Ｏ至混合溶剂(Ｈ2ＯＤＭＦ)的标准迁移自由能ΔＧｔ及其温度系数,计算ＲｂＣｌ的标准迁移熵ΔＳｔ.结果尚未见…     

蛋白质在固定Zn2+金属螯合亲和色谱中的变性热力学

在15~85℃宽温度范围,研究了蛋白质在固定Zn2 金属螯合色谱系统中的热行为和变性热力学。实验结果表明,蛋白质在色谱过程都有一个固定的热转变温度:核糖核酸酶(RNase)、α-胰凝乳蛋白酶原A(α-Chy)的热转变温度约为55℃,细胞色素C(Cyt-C)和溶菌酶(Lys)约为65℃;,热转变温度的出现标志蛋白质构象发生变化;利用Van′tHoff作图测定了蛋白质在色谱系统热变性时的标准焓变ΔH°和标准熵变ΔS°,提出用标准熵变ΔS°和自由能变ΔG°判断蛋白质构象变化;利用ΔH°-ΔS°的线性关系估算了蛋白质热变性时的补偿温度,鉴定了蛋白质各变体在金属螯合色谱中保留机理的同一性,RNase、Cyt-C、Lys和α-Chy的补偿温度分别为55℃、65.8℃、65.2℃和54.8℃;根据蛋白质热变性时的补偿温度和构象变化熵变Δ(ΔS°)的大小,讨论了蛋白质在阳离子交换色谱和固定Zn的金属螯合色谱体系中的热稳定性。实验证明,在IDA裸柱引入Zn2 后蛋白质在色谱系统中的热稳定性减小,平均补偿温度从65.3℃降低到59.7℃,而构象变化熵变的绝对值大幅度升高。     

PuC2 气态分子的结构与热力学稳定性研究

在相对论有效原子实势近似下,用密度泛函B3LYP方法,求得PuC2气态分子的结构与不同温度下的热力学函数.根据热力学原理,计算得到PuC2气态分子在不同温度下的标准生成自由能变均为较大正值,据此说明, PuC2气态分子不具有热力学稳定性.     

The effect of carbonyl carbon atom replacement in acetone molecule (ACN) by sulfur atom (DMSO): Part II. Thermodynamic functions of complex formation of crown ethers with Na<Superscript>+</Superscript> in mixed solvents

The thermodynamic functions of complex formation of benzo-15-crown-5 ether (B15C5) and sodium cation (Na⁺) in acetone–water mixtures at 298.15 K have been calculated. The equilibrium constants of B15C5/Na⁺ complex formation have been determined by conductivity measurements. The enthalpic effect of complex formation has been measured by the calorimetric method. The complexes are enthalpy-stabilized but entropy-destabilized in acetone–water mixtures. The effects of hydrophobic hydration, preferential solvation of B15C5 by a molecule of water and acetone, respectively and the solvation of Na⁺ on the complex formation processes have been discussed. The calculated thermodynamic functions of B15C5/Na⁺ complex formation and the effect of benzene ring on the complex formation have been compared with analogous data obtained in dimethylsulfoxide–water mixtures. The effect of carbonyl atom replacement in acetone molecule by sulphur atom (DMSO molecule) on the thermodynamic functions of complex formation has been analysed.     

Pu（^7Fg）＋H2（X^1∑g^＋,0,0）的分子反应动力学

基于PuH_2分子基态(X~7A_1)的分析势能函数，用准经典的Monte-Carlo轨线法 对Pu(~7Fg)+H_2(X~1∑_g~+，0，0)的分子反应动力学过程进行了计算。结果表明 ：Pu(~7F_g)与H_2(X~1∑_g~+，0，0)碰撞是弹性碰撞。     

分子C_(60)CH_2(C_(2V))气相热力学性质的理论研究

自从富勒烯被发现并能常量制备以来,人们就开始了对Ｃ６０衍生物的研究．Ｃ６０ＣＨ２是Ｃ６０最简单的衍生物之一,Ｃ６０ＣＨ２有２种异构体,根据所属点群的对称性划分一种是属Ｃ２Ｖ群的Ｃ６０ＣＨ２（Ｃ２Ｖ）,另一种是属ＣＳ群的Ｃ６０ＣＨ２（ＣＳ）．文献［１］...     

Ab initio theoretical study of temperature and density dependence of molecular and thermodynamic properties of water in the entire fluid region: autoionization processes

The temperature and density dependence of the molecular and thermodynamic properties of water is investigated theoretically by means of the ab initio electronic structure theory combined with the reference interaction site model method, so-called RISM-SCF. We consider the autoionization process (H2O + H2O right harpoon over left harpoon H3O+ + OH-) by regarding H2O, H3O+, and OH- as "solute" molecules in an aqueous solution and evaluate molecular geometry, electronic structure, solvation structure, and the ionic product of water (pKw) of these species as functions of thermodynamic conditions. In our previous paper, we calculated these properties by using essentially the same method in a wide range of density values (0.6-1.4 g/cm3). However, the calculation was limited at rather higher density (>0.6 g/cm3) due to the difficulty of convergence, which is inherent to the hypernetted-chain (HNC) closure. The problem is overcome in this study by employing the Kovalenko-Hirata (KH) closure which hybridizes the HNC and the mean-spherical approximation (MSA). Here, we present the results for the thermodynamic range of densities from 0.025 to 1.0 g/cm3 and for temperatures from 300 to 800 K including the supercritical point.     

Cucurbit[6]uril as Ligand for the Complexation of Diamines, Diazacrown Ethers and Cryptands in Aqueous Formic Acid

The complex formation between cucurbit[6]uril and different diamines, diazacrown ethers, and cryptands has been studied in aqueous formic acid solution. The complex stabilities and the thermodynamic values for the complex formation of diamines are reduced if any further donor atom (e.g., sulfur, oxygen, or nitrogen) is present in the molecules. The inclusion of this polar group inside the cavity of cucurbit[6]uril has a negative effect upon the complex formation. Diazacrown ethers and cryptands do not form inclusive complexes. One nitrogen donor atom interacts with the carbonyl groups at one of the portals.     

Quantum chemical calculation studies on 4-phenyl-1-(1-phenylethylidene)thiosemicarbazide

Ab initio calculations of the structure, atomic charges, natural bond orbital and thermodynamic functions have been performed at HF/6-311G^** and B3LYP/6-311G^** levels of theory for the title compound of 4-phenyl-1-(1-phenylethylidene) thiosemicarbazide. The calculated results show that the sulfur atom and all of the nitrogen atoms have bigger negative charges and that they are the potential sites to react with the metallic ions, which make the title compound a multidentate ligand. The coordination ability of the sulfur atom and the nitrogen atom of C=N double bond increases with the increase of polarity of the solvent. Electronic absorption spectra have been calculated by time-dependent density functional theory (TD-DFT) method. The calculation of the second-order optical nonlinearity has also been carried out with the PM3 semi-empirical method, resulting in the molecular hyperpolarisability is 5.477×10⁻³⁰ esu.     

A morphometric approach for the accurate solvation thermodynamics of proteins and ligands

We have developed a versatile method for calculating solvation thermodynamic quantities for molecules, starting from their atomic coordinates. The contribution of each atom to the thermodynamic quantities is estimated as a linear combination of four fundamental geometric measures of the atomic species, which are defined by Hadwiger's theorem, and the coefficients reflecting their solvation properties. This treatment enables us to calculate the solvation free energy with high accuracy despite of the limited computational load. The method can readily be applied to macromolecules in an all‐atom molecular model, allowing the stability of these molecules' structures in solution to be evaluated. © 2013 Wiley Periodicals, Inc.     

Quantum Chemical Calculation Studies on 4-Phenyl-1-(Propan-2-Ylidene)Thiosemicarbazide

Ab initio calculations of the structure, atomic charges, natural bond orbital, and thermodynamic functions have been performed at HF/6-311G^∗∗ and B3LYP/6-311G^∗∗ levels of theory for the title compound of 4-phenyl-1-(propan-2-ylidene)thiosemicarbazide. The calculated results show that the sulfur atom and all of the nitrogen atoms have bigger negative charges and they are the potential sites to react with the metallic ions, which make the title compound become a multidentate ligand. The coordination ability of the sulfur atom and the nitrogen atom of C=N double bond will increase with the increase of the polarity of the solvent. Electronic absorption spectra have been calculated by time-dependent density functional theory (TD-DFT) method. The calculation of the second-order optical nonlinearity also has been carried out, and the molecular hyperpolarizability is 3.068×10⁻³⁰ esu.