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Based on zero-order Bragg-Williams approximation, a new statistic thermodynamic model is presented herein. The distinctive feature of the new model is that an apparent compressibility factor α is introduced to correct the volume change of high-pressure gases and ensure no loop-like curves are obtained in the fitting results. The new model is successfully applied to investigate hydrogen absorption on metal powders. Our results indicate that the model works very well and can be used to predict PCT curves at different temperatures. Hence, our new model exhibits significant potential for application in practical systems. 相似文献
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硝基氢异构化反应的理论研究 总被引:2,自引:0,他引:2
The isomerization of singlet, nitryl hydride (HNO2) has been studied by using ab initio method at MP2 level with 6-31G* basis set. The calculation indicates that the reaction is exothermic by 10.8kJ.mol-1, the energy barrier is 227.9kJ•mol-1, and nitryl hydride is not easily isomerized to trans-HONO. 相似文献
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本文采用自洽场分子轨道UHF/6-31G从头计算法, 辅以能量梯度法研究气相烯丙醇光异构化反应的机理。全部优化了T1态势能面上反应物、过渡态、中间体和产物的几何构型。基于Fukui提出的内禀反应坐标理论(IRC)计算这一体系的反应途径, 并针对各驻点进行MP2/6-31G的相关能校正, 得到该反应在激发态进行并为一经历双自由基中间体的分步反应的结论。支持了实验工作者提出的机理。 相似文献
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N-甲硝胺二聚体分子间相互作用的理论研究 总被引:5,自引:1,他引:5
用ab initio方法,在HF/6-31G水平下求得N-甲硝胺二聚体势能面上3种优化构型,经MP4和MP2校正电子相关能及校正基组叠加误差(BSSE),求得分子间最大相互作用能为-18.81kJ.mol^-1,甲基内旋转对相互作用能影响较大,在标准状态下,由单体形成最稳定二聚体的自由能变化为10.02kJ.mol^-1,同时还讨论了温度对过程的影响。 相似文献
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F原子与瞬态自由基CH_2SH反应的理论研究 总被引:1,自引:0,他引:1
用量子化学从头算和密度泛函理论(DFT)对F原子与自由基CH_2SH在势能面上 的反应进行了研究。在B3LYP/6-311G水平上计算出了各物种的优化构型、振动频率 和零点振动能(ZPVE);各物种的总能量由B3LYP/6-311 + G(2df, pd)//B3LYP/6- 311G计算,另外对反应物和产物还计算了其G3能量。结果表明:首先F通过与C或S 结合的两种途径与CH_2SH相配位,再通过H(4)原子转移形成甲基,然后甲基再旋 转,甲基中H(4)原子最终与F结合,反应产物为HF和CH_2S。反应为放热反应,分 别为ΔH_r = -370.7 kJ/mol (DFT)和-396.94 kJ/mol (G3)。此外依据计算出的反 应热,可得自由基·CH_2SH的生成热Δ_fH°_(298.15) = 146.44 kJ/mol (DFT), 而Δ_fH°_0 = 167.36 kJ/mol (G3)。它们与以前的实验和理论值是一致的。 相似文献
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锆钴合金氢化反应热力学函数的计算 总被引:14,自引:0,他引:14
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. 相似文献
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An-yong Li Li-fang Xu Zhou Ling 《化学物理学报(中文版)》2009,22(1):57-62
The dihydrogen bonds B-H...H-X (X= the complexes of NH3BH3 with HF, HCl, F, Cl, Br, C, O, N) in the dimer (NH3BH3)2 and HBr, H2CO, H20, and CH3OH were theoretically studied. The results show that formation of the dihydrogen bond leads to elongation and stretch frequency red shift of the BH and XH bonds, except that in the H2CO system, the CH bond blue shifts. For (NH3BH3)2 and the complexes of the halogenides, red shifts of the XH bonds are caused by the intermolecular hyperconjugation σ(BH)→σ^* (XH). For the system of H2CO, a blue shift of the CH bond is caused by a decrease of the intramolecular hyperconjugation n(O→σ^* (CH). In the other two systems, the red shift of OH bond is a secondary effect of the stronger traditional red-shifted H-bonds N-H... O. In all these systems, red shifts of the BH bonds are caused by two factors: negative repolarization and negative rehybridization of the BH bond, and decrease of occupancy on σ(BH) caused by the intermolecular hyperconjugation σ(BH)→σ^* (XH). 相似文献
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A modified Miedema model, using interrelationship among the basic properties of elements Ti and H, is employed to calculate the standard enthalpy of formation of titanium hydride TiHx (1≤x≤2). Based on Debye theories of solid thermal capacity, the vibrational entropy, as well as electronic entropy, is acquired by quantum mechanics and statistic thermodynamics methods, and a new approach is presented to calculate the standard entropy of formation of TiH2. The values of standard enthalpy of formation of TiHx decrease linearly with increase of x. The calculated results of standard enthalpy, entropy, and free energy of formation of TiH2 at 298.16 K are -142.39 kJ/mol, -143.0 J/(mol?K) and -99.75 kJ/mol, respectively, which is consistent with the previously-reported data obtained by either experimental or theoretic 相似文献
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While the sonochemical grafting of molecules on silicon hydride surface to form stable Si–C bond via hydrosilylation has been previously described, the susceptibility towards nucleophilic functional groups during the sonochemical reaction process remains unclear. In this work, a competitive study between a well-established thermal reaction and sonochemical reaction of nucleophilic molecules (cyclopropylamine and 3-Butyn-1-ol) was performed on p-type silicon hydride (111) surfaces. The nature of surface grafting from these reactions was examined through contact angle measurements, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Cyclopropylamine, being a sensitive radical clock, did not experience any ring-opening events. This suggested that either the Si–H may not have undergone homolysis as reported previously under sonochemical reaction or that the interaction to the surface hydride via a lone-pair electron coordination bond was reversible during the process. On the other hand, silicon back-bond breakage and subsequent surface roughening were observed for 3-Butyn-1-ol at high-temperature grafting (≈150 °C). Interestingly, the sonochemical reaction did not produce appreciable topographical changes to surfaces at the nano scale and the further XPS analysis may suggest Si–C formation. This indicated that while a sonochemical reaction may be indifferent towards nucleophilic groups, the surface was more reactive towards unsaturated carbons. To the best of the author’s knowledge, this is the first attempt at elucidating the underlying reactivity mechanisms of nucleophilic groups and unsaturated carbon bonds during sonochemical reaction of silicon hydride surfaces. 相似文献
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An approach is proposed for the quantum-chemical investigation of “hydride ion” transfer based on analysis of the similarity
of the order of variation in the ionization potentials, enthalpies, and free energies of affinity to the hydride ion, the
hydrogen atom, and the proton in the substrate molecules and also the derivatives of their cations, radicals, and ions to
the experimentally established “hydride” series. It was established that the experimental “hydride” mobility series of six
chalcogenopyrans based on “semicyclic” 1,5-diketones agrees with the quantum-chemically calculated ionization potentials of
the molecules and with the affinity of the respective radicals to the hydrogen atom participating in the transfer. It was
found that direct removal of a hydride ion and initial deprotonation of the substrates followed by the removal of two electrons
are unlikely. “Hydride” shift mechanisms, in which the first stage is transfer of an electron or hydrogen atom from the chalcogenopyran
molecules, are feasible.
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Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1305–1311, September, 2005. 相似文献
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实验提示应用248 nm UV波长对HCNO分子进行直接光解, 该分子可能发生裂解, 得到某些产物. 为了揭示HCNO分子的裂解机理, 选择HCNO分子的一组相对能级作为理论研究的起始点, 即1A' (0.00 kJ/mol), 3A' (255.01 kJ/mol), 3A" (282.37 kJ/mol)和1A" (341.59 kJ/mol), 进而找到了合理的反应路径, 阐明了相应的裂解机理, 得到的主要产物为H+NCO, HCN+O和NH+CO, 与实验提示的结果相符合. 相似文献
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ATheoreticalStudyontheHydrogen-bondedDimersofHNCOMoleculesWangYan;FengWen-Lin;ZhangShao-Wen;ZhuWei-Xin(ChemistryDepartment,Be... 相似文献
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Patricia Lara Margarita Paneque Prof. Dr. Manuel L. Poveda Prof. Dr. Laura L. Santos Dr. José E. V. Valpuesta Verónica Salazar Dr. Ernesto Carmona Prof. Dr. Salvador Moncho Gregori Ujaque Dr. Agustí Lledós Prof. Dr. Celia Maya Dr. Kurt Mereiter Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(36):9046-9057
Experimental and theoretical studies on equilibria between iridium hydride alkylidene structures, [(TpMe2)Ir(H){?C(CH2R)ArO }] (TpMe2=hydrotris(3,5‐dimethylpyrazolyl)borate; R=H, Me; Ar=substituted C6H4 group), and their corresponding hydride olefin isomers, [(TpMe2)Ir(H){R(H)C? C(H)OAr}], have been carried out. Compounds of these types are obtained either by reaction of the unsaturated fragment [(TpMe2)Ir(C6H5)2] with o‐C6H4(OH)CH2R, or with the substituted anisoles 2,6‐Me2C6H3OMe, 2,4,6‐Me3C6H2OMe, and 4‐Br‐2,6‐Me2C6H2OMe. The reactions with the substituted anisoles require not only multiple C? H bond activation but also cleavage of the Me? OAr bond and the reversible formation of a C? C bond (as revealed by 13C labeling studies). Equilibria between the two tautomeric structures of these complexes were achieved by prolonged heating at temperatures between 100 and 140 °C, with interconversion of isomeric complexes requiring inversion of the metal configuration, as well as the expected migratory insertion and hydrogen‐elimination reactions. This proposal is supported by a detailed computational exploration of the mechanism at the quantum mechanics (QM) level in the real system. For all compounds investigated, the equilibria favor the alkylidene structure over the olefinic isomer by a factor of between approximately 1 and 25. Calculations demonstrate that the main reason for this preference is the strong Ir–carbene interactions in the carbene isomers, rather than steric destabilization of the olefinic tautomers. 相似文献