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1.
本文就SiH4与HX形成的二氢键复合物的结构特征及本质进行了探讨。在MP2/6-311++G(3d,3p)水平优化、频率验证得到复合物的分子结构,通过分子间距离及电子密度等值线图,我们确认SiH4与卤化氢已形成了二氢键复合物。MP2/6-311++G(3d,3p)水平下进行BSSE校正后的结合能为2.703-4.439 KJ/mol。用对称匹配微绕理论(SAPT)对结合能进行分解,分解结果显示,SiH4匟X(X=F,Cl,Br,I)二氢键复合物中静电能对总吸引能的贡献小于28%,并且相对稳定,这就是说SiH4匟X二氢键复合物的本质并非静电作用,而是静电能、诱导能、色散能、交换能对总结合能的贡献都非常重要。 相似文献
2.
刘红;陈燕芹;王一波 《化学学报》2008,66(3):301-307
本文就SiH4与HX形成的二氢键复合物的结构特征及本质进行了探讨。在MP2/6-311++G(3d,3p)水平优化、频率验证得到复合物的分子结构,通过分子间距离及电子密度等值线图,我们确认SiH4与卤化氢已形成了二氢键复合物。MP2/6-311++G(3d,3p)水平下进行BSSE校正后的结合能为2.703-4.439 KJ/mol。用对称匹配微绕理论(SAPT)对结合能进行分解,分解结果显示,SiH4匟X(X=F,Cl,Br,I)二氢键复合物中静电能对总吸引能的贡献小于28%,并且相对稳定,这就是说SiH4匟X二氢键复合物的本质并非静电作用,而是静电能、诱导能、色散能、交换能对总结合能的贡献都非常重要。 相似文献
3.
对BeH2与HX(X=F, Cl, Br, I)形成的二氢键复合物的结构特征及本质进行了探讨. 在MP2/6-311++G(3d,3p)水平优化、频率验证, 得到复合物的分子结构, 用分子间距离及电子密度拓扑理论确认BeH2与卤化氢已形成了二氢键型复合物. 在MP2/6-311++G(3d, 3p)水平下进行基函数重叠误差(BSSE)校正后的结合能在-14.468 kJ·mol-1到-5.464 kJ·mol-1之间.用对称匹配微扰理论(SAPT)对复合物的结合能进行分解, 结果表明, BeH2…HX二氢键复合物中静电能对总吸引能的贡献都是最主要的, 但交换排斥能、诱导能、色散能对总结合能的贡献也很重要. 从BeH2…HF到BeH2…HI, 诱导能对总吸引能的贡献从37.8%逐渐减小到24.0%. 而色散能对总吸引能的贡献从BeH2…HF体系中的16.0%逐渐增加到BeH2…HI体系中的33.8%. 相似文献
4.
对GeH4与HX形成的二氢键复合物的结构特征及本质进行了探讨.在MP2/6-311 ++G(3 d,3p)水平优化、频率验证得到复合物的分子结构,通过分子的几何参数及电子密度拓扑分析,确认GeH4与卤化氢已形成了二氢键复合物.MP2/6-311 ++ G(3d,3p)水平下进行BSSE校正后的结合能为3.281到4.5... 相似文献
5.
在MP2水平上,采用全电子基组,对C2H2与HX(X=F,Cl,Br,I)相互作用进行了研究.构型优化同时进行频率验证,得到4个T型结构的稳定复合物,相互作用能在-12.761~-7.086kJ/mol之间.自然键轨道(NBO)与分子中的原子(AIM)理论分析表明,形成复合物分子间的电荷转移量都很少,最大仅为0.009a.u.,作用强度与氢键类似.对称性匹配微拢理论(SAPT)能量分解数据表明,对于C2H2…HX(X=F,Cl,Br,I)体系,从F到I,静电作用逐渐减弱,色散作用逐渐增强;相互作用能中对吸引能的贡献主要为静电能和色散能,二者之和占到80%以上,诱导能所占的比例很小,卤化氢与乙炔分子间相互作用的本质为静电作用和色散作用. 相似文献
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用对称性匹配微扰理论(SAPT)对C2H2与X2(X=F,CI,Br,I)相互作用进行了量子化学研究.优化所得的4个稳定复合物相互作用能在-3.276 8~-10.639 5 kJ/mol之间.自然键轨道(NBO)理论分析表明,形成复合物分子间的电荷转移量都很少,在0.002 3~0.013 2之间.SAPT2能量分析显示,从F到I,静电能和诱导能先增大后减小,交换能和色散能逐渐增强,相互作用能依次增强.复合物稳定构型的相互作用能中静电能占主导作用,对吸引能的贡献比例在C2H2…F2中最大(57.3%),在C2H2…I2中最小(49.7%);其次为色散能,在吸引能中所占的比例在21.9%(C2H2…F2)~31.2%(C2H2…I2)之间;诱导能在吸引能中所占的比例最小,均小于20.7%. 相似文献
8.
采用从头算方法对SiH4与AB型卤素互化物(ClF、BrF、IF、ICl、IBr、BrCl)形成的复合物的结构特征及本质进行了探讨.在MP2/6-311++G(3d,3p)水平上优化复合物的分子结构,并进行频率验证.通过分子间距离、自然键轨道(NBO)净电荷迁移数及分子图,确认SiH4与卤素互化物形成反转氢键型复合物.在MP2/6-311++G(3d,3p)水平上进行基组重叠误差(BSSE)校正后的作用能为-5.113--9.468kJ·mol-1.用对称匹配微扰理论(SAPT)对作用能进行分解,结果显示,诱导能对总吸引能的贡献在55.0%到72.2%之间,是最主要的贡献部分,静电能和色散能对总吸引能的贡献都小于25.0%. 相似文献
9.
在MP2水平下对被定义为"电荷转移复合物(CTC)"的苯(C6H6)-卤素分子X2(X=F, Cl, Br, I)相互作用体系进行了量子化学研究. 在优化所得C6H6-X2(X=F, Cl, Br, I)复合物的平衡几何结构中, 卤素分子X2接近垂直指向苯环上碳-碳双键的中心. 自然键轨道(NBO)分析结果表明, 苯-卤素体系中电荷转移的数量很少. 对称性匹配微扰理论(Symmetry-adapted perturbation theory, SAPT) 能量分解结果显示, 在4个复合物体系中, 静电作用的贡献相对较小(只占总吸引作用的20%左右), 对于C6H6-F2体系, 色散作用是其主要吸引作用, 对于C6H6-Cl2, C6H6-Br2和C6H6-I2 体系, 诱导作用则是其主要的吸引作用, 从F到I, 色散作用逐渐减弱, 诱导作用逐渐增强, 表明在电子相关水平上将苯-卤素体系称为"电荷转移复合物"的说法并不确切. 相似文献
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Absolute reaction rates for F + HX and F + DX (X = I, Br, Cl) have been obtained by monitoring the rise time of HF (DF) vibrational fluorescence following multiphoton dissociation of SF6 in mixtures of HX (DX) and argon. The cross sections for reaction are, in units of 10?16 cm2, 4.37, 5.26, and 1.16 for HI, HBr, and HCl, respectively. The isotope effects kHX/kDX, are 1.29 ± 0.14, 1.29 ± 0.18, and 1.38 ± 0.29, respectively. 相似文献
12.
Ab initio calculations were carried out for the reactions of silane and halosilanes (SiH3X, X=H, Cl, Br, I) with HCN. Geometries of the reactants, transition states, intermediates and products were optimized at HF, MP2, and B3LYP levels of theory using the 6-31G(d) and 6-31G(d,p) basis sets. Energies were also obtained using G3MP2 and G3B3 levels of theory. Intrinsic reaction coordinate (IRC) calculations were performed to characterize the transition states on the potential energy surface. It was found that HCN can react with silane and halosilanes via three different mechanisms. One involves HX elimination by a one-step pathway producing SiH3CN. The second mechanism consists of H2 elimination, producing SiH2XCN via a one-step pathway or three multiple-step pathways. The third mechanism involves dissociation of SiH3X to various products, which can then react with HCN. Activation energies, enthalpies, and free energies of activation along with the thermodynamic properties (DeltaE, DeltaH, and DeltaG) of each reaction pathway were calculated. The reaction of SiH3X with HCN produce different products depending on substituent X. We have found that the standard 6-31G(d) bromine basis set gave results which were in better agreement with the G3MP2 results than for the Binning-Curtiss basis set. Computed heats of formation (DeltaHf) for SiH3CN, SiH3NC, SiH2ClCN, SiH2BrCN, SiH2ICN, SiHCl, SiHBr, and SiHI were found to be 133.5, 150.8, -34.4, 23.6, 102.4, 48.7, 127.1, and 179.8 kJ mol-1, respectively. From enthalpies calculated at G3MP2, we predict that the DeltaHf for SiH2 to be 262.8 kJ mol-1 compared to the experimental value of 273.8+/-4.2 kJ mol-1. 相似文献
13.
Franz Pertlik 《Monatshefte für Chemie / Chemical Monthly》1988,119(4):451-456
The crystal structures of five isotypic hexagonal compounds with general formulaMAs4O6
X [M=K, NH4;X=Cl, Br, I; space group: P622;Z=1] were determined from 370 single crystal X-ray data and refined toR values <0.05. The structure type is characterized by neutral charged
[As2O3] sheets arranged parallel (00.1). The As atoms of neighbouring two sheets point to each other and the sheets are combined by interlayeredM andX atoms, respectively. TheM atoms are coordinated to twelve oxygen atoms, theX atoms are coordinated to twelve arsenic atoms. In both cases the coordination polyhedron is a hexagonal prism. The compounds were synthesized by thermal treatments of cubic As2O3 and potassium or ammonium haloids in a saturated aqueous solution of potassium acetate resp. ammonia [500 K, saturation vapour pressure].
Die Verbindungen KAs4O6 X (X=Cl, Br, I) und NH4As4O6 X (X=Br, I): Hydrothermalsynthese und Strukturbestimmung
Zusammenfassung Die Kristallstrukturen der fünf isotypen hexagonalen Verbindungen mit der allgemeinen FormelMAs4O6 X [M=K, NH4;X=Cl, Br, I; Raumgruppe: P622;Z=1] wurden anhand von 370 Einkristall-Röntgendaten bestimmt und aufR-Werte <0.05 verfeinert. Der Strukturtyp ist ausgezeichnet durch neutrale [As2O3]-Schichten, die parallel (00.1) angeordnet sind. Die As-Atome zweier benachbarter Schichten weisen jeweils aufeinander zu, und die Schichten selbst werden durch zwischengelagerteM- bzw.X-Atome verbunden. DieM-Atome werden jeweils von zwölf O-Atomen, dieX-Atome von zwölf As-Atomen umgeben. Das Koordinationspolyeder ist in beiden Fällen ein hexagonales Primsa. Die einzelnen Verbindungen wurden unter Hydrothermalbedingungen aus kubischem As2O3 und dem jeweiligen Kalium- oder Ammoniumhalogenid in einer gesättigten wäßrigen Lösung von Kaliumacetat bzw. Ammoniak synthetisiert (500 K, Sättigungsdampfdruck).相似文献
14.
Calculations are reported on the molecular force fields of sulphuryl fluoride and sulphuryl chloride, using new data for the fluoride and a modified geometry for the chloride. Further calculations were performed for the mixedhalides SO2XF (X = Cl, Br) on the basis of data and structural proposals of Birchall and Gillespie as well as Reed and Lovejoy. 相似文献
15.
Martin J. Packer Erik K. Dalskov Stephan P. A. Sauer Jens Oddershede 《Theoretical chemistry accounts》1994,89(5-6):323-333
Summary We report values of the correlated dynamic dipole polarizability for the halides HX and CH3X (X = F, Cl and Br). The polarizabilities are calculated within the second-order polarization propagator approximation (SOPPA). The correlated results are in much better agreement with the available experimental results, compared to RPA. We also report the second-order dipole moments using both the relaxed and unrelaxed MP2 density matrices. The relaxed results are in better agreement with experiment. 相似文献
16.
Vibrational Spectra of the Cluster Compounds (M6X12i) · 8H2O, M = Nb, Ta; Xi = Cl, Br; Xa = Cl, Br, I IR and, for the first time, Raman spectra at 80 K of the cluster compounds (M6X)X · 8H2O; M = Nb, Ta; Xi = Cl, Br; Xa = Cl, Br, I, have been recorded, characterized by typical frequencies of the (M6X) unit, which are only slightly influenced by the terminal Xa ligands. The most intense line with the depolarisation ≈? 0.2 in all Raman spectra is caused by inphase movement of all atoms and assigned to the symmetric metal-metal vibration v1, observed for the clusters (Nb6Cl) at 233–234, for (Nb6Br) at 186–187, for (Ta6Cl) at 199–203, and for (Ta6Br) at 176–179 cm?1. The IR spectra exhibit in the same series intense bands at 233, 204, 207, and 179 cm?1, assigned to the antisymmetric metal-metal vibration. The metal-metal frequencies are significantly higher than discussed before. The tantalum clusters show on excitation with the krypton line 647.1 nm in the region of a d–d transition at 645 nm a resonance Raman effect with series of overtones and combination bands. In case of (Ta6Br) another polarisized band is observed at 229 cm?1 and assigned to the Ta? Bri vibration v2. From the progressions of v1 and v2 anharmonicity constants of about ?3 cm?1 are calculated indicating a strong distortion of the potential curves. 相似文献
17.
LIN Chen-Sheng LI Jun LIU Chun-WanFujian Institute of Research on the Structure of Matter Chinese Academy of Sciences State Key Laboratory of Structural Chemistry Fuzhou Fujian China 《中国化学》1994,12(4):305-313
The molecular orbitals for B4H4, B4F4, B4Cl4, B4Br4 and B4I4 have been calculated by using all-electron or effective core potential ab initio method at the self-consistent field level using basis sets with diffuse and polarization functions. The boron-boron and boron-halide (-hydrogen) distances of these cage compounds are optimized with three kinds of basis sets constrained to a tetrahedral symmetry. According to the localization scheme of Boys, four three-centered two-electron (3c2e) B-B-B bonds localized on each of the faces of the B4 tetrahedron are derived for B4X4 clusters. The HOMO-LUMO energy gaps, atomization energies and Mulliken overlap populations of these compounds indicate that the stabilities of the clusters decrease in the sequence of B4F4 > B4Cl4, B4H4 > B4Br4 > B4I4. 相似文献
18.
Inhaltsübersicht. Synthese (aus den Elementen; Einkristalle durch Sublimation im Gradienten: 200 → 100°C) und Strukturverfeinerung von InI (orthorhombisch, Cmcm, Z = 4; a = 476,3(1); b = 1278,1(1); c = 490,9(1) pm) werden beschrieben. Ein Vergleich mit InBr und InCl (alle TlI-Typ) weist auf die Bedeutung des 5s2-Elektronenpaares von In+ für diesen Strukturtyp und auf attraktive Wechselwirkungen in Richtung auf die Ausbildung eines Dimeren, In22+, hin. Note on the Red Monohalides of Indium, InX (X = CI, Br, I) Synthesis (from the elements; single crystals by sublimation in a 200 → 100°C gradient) and structure refinement of InI (orthorhombic, Cmcm, Z = 4, a = 476.3(1), b = 1278.1(1), c = 490.9(1) pm) are reported. A comparison with the isotypic halides InBr and InCl (all TlI type) hints at the importance of the 5s2 electron pair of In+ for this structure type. Attractive interactions in the direction of the formation of a dimer, In22+, could play a role. 相似文献