首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到19条相似文献,搜索用时 250 毫秒
1.
采用[CCSD(T)]-F12方法和aug-cc-pVTZ基组,同时引入中心键函数(3s3p2d1f1g)构建了Kr-C2H2体系的高精度四维势能面.在构建势能面时考虑了分子间的振动方式及C2H2单体内的ν1对称伸缩和ν3反对称伸缩振动.将计算得到的四维势能面在Q1方向和Q3方向分别做积分得到C2H2单体分别处于振动基态和(ν1,ν3)=(1,1)激发态的平均势能面.计算结果表明,这2个平均势能面均存在2个等价的T型全局极小值和2个等价线性极小值.全局极小值的几何构型位于R=0.41 nm,θ=65.6°/114.4°,势阱深度为151.88 cm-1.对径向部分采用离散变量表象法(DVR),角度部分采用有限基组表象法(FBR),并结合Lanczos循环算法计算了Kr-C2H2的振转能级和束缚态.计算结果表明,复合物在(ν1,ν3)=(1,1)区域的带心位移为-1.48 cm-1,表现为红移,与实验值-1.38 cm-1很接近;计算得到的红外跃迁频率也与实验值相吻合,说明得到的从头算势能面具有高精度.  相似文献   

2.
噻吩光解反应机理的理论研究   总被引:1,自引:0,他引:1  
使用密度泛函理论(DFT)中的B3LYP方法, 采用6-31G**和6-31++G**基组, 对噻吩的光解反应进行了理论研究. 对照实验结果, 我们研究了五个光解通道, 包括生成C4H4+S, C2H2+C2H2S和CS+C3H4的三个闭壳层分子解离通道与生成HCS+C3H3和HS+C4H3的自由基解离通道. 各个可能的反应通道的产物碎片的具体形式得到了确认. 研究发现在基态生成C2H2+C2H2S和在最低三态生成C4H4+S的反应从能量上考虑最为有利, 而实验上观测到的主要产物C2H2+C2H2S主要是在基态上产生的. 通过对比实验结果与计算结果, 我们认为噻吩光解反应机理与所用激发光波长有关.  相似文献   

3.
皮瑛瑛  尚亚卓  刘洪来  胡英 《化学学报》2005,63(14):1281-1287
摘要 采用荧光探针法和电导法研究了正离子偶联表面活性剂(C12H25(CH3)2N-(CH2)6-N(CH3)2C12H25•2Br) (12-6-12• 2Br)和带相反电荷聚电解质聚丙烯酸钠(NaPA)的相互作用, 结果表明: 由于静电相互作用, 12-6-12•2Br和NaPA之间可以形成类胶束或复合物. 对比十二烷基三甲基溴化铵(DTMAB)与NaPA复配体系的荧光光谱, 发现偶联表面活性剂与NaPA的相互作用强于传统表面活性剂. 此外, 还研究了盐和醇对偶联表面活性剂/聚丙烯酸钠的复配体系微极性的影响, 发现盐和醇对表面活性剂在聚电解质上形成类胶束和复合物的溶解都有一定的促进作用.  相似文献   

4.
采用密度泛函理论PBE0方法, 在aug-cc-pVTZ水平上理论预测了含平面五配位硅和锗原子的XBe5H6 (X=Si, Ge)团簇. 势能面系统搜索及高精度量化计算表明, 它们均为全局极小结构. XBe5H6(X=Si, Ge)团簇整体呈完美的扇形结构: Si/Ge原子被5个金属Be原子配位; 4个H原子以桥基方式与Be原子相键连, 剩余的2个 H原子以端基方式与两端的Be原子成键. 化学键分析表明, XBe5H6(X=Si, Ge) 团簇中XBe5单元具有完全离域的1个π及3个σ键, 外围铍氢间形成4个Be—H—Be 三中心二电子(3c-2e)键及2个定域的Be—H键. XBe5单元上离域的2π及6σ电子赋予体系πσ双重芳香性, 并使Si/Ge原子满足八隅律(或八电子规则). 能量分解-化学价自然轨道分析揭示, Si/Ge和Be5H6之间主要为电子共享键.  相似文献   

5.
炼厂干气中回收乙烯是扩宽C2H4来源的有效途径,但C2H4和C2H6物理性质和分子尺寸非常接近,分离困难.金属有机骨架材料(MOFs)近年来在低碳烃分离领域展现出广阔的前景.本工作采用氨吸附改性调节UTSA-280的结构,通过一维直孔道大小的调节实现C2H4/C2H6的高效分离.改性后的UTSA-280具有独特的超微孔结构能提升C2H4的吸附,而完全不吸附稍大的C2H6,实现理想的C2H4/C2H6吸附选择性(>1000).结果表明,改性后的UTSA-280的C2H4吸附量可提高至2.83 mmol/g,与未改性的材料相比增加29%,并且能阻挡C2H6的吸附,最终达到>1200的C2H4/C2H6选择性.蒙特卡罗分子模拟(GCMC)计算C2H4/C2H6混合气体(1:1)的吸附得出,改性后UTSA-280孔内的C2H4吸附相比于C2H6具有更多的吸附分布.通过C2H4/C2H6混合气体穿透实验测试,改性后的UTSA-280材料能展现出48 min以上的分离时间,相比于未改性的材料,分离性能提升近1倍.  相似文献   

6.
用分子力学方法对一些金属汞化合物进行了探讨和研究.通过与参考体系对比以及内旋转势垒计算的方式,说明了在诸如cis-ClHgCHCHCl(Ⅰ),o-C6H4HgCl2(Ⅵ),Cl_Hg_CH2_CH2_CN(Ⅶa),Cl_Hg_CH2_CH2_C6H5(Ⅺa)分子中,非相邻的Cl,Hg原子间存在着弱相互作用.  相似文献   

7.
根据原子价的量子化学定义,采用3-21G基组的ab initio方法,对B2H6及其桥原子取代物H4B2X2(X=F,Cl,OH,NH2,CH3)进行几何构型优化,讨论桥原子的成键特征,并计算了B4H10、B5H9和B5H11等硼氢化合物的原子价,讨论了它们的亲电和亲核取代反应活性。  相似文献   

8.
郝海燕  刘振  祖莉莉 《物理化学学报》2015,31(11):2029-2035
有机硫化物是大气主要污染物之一,其在大气中的光解产物还将造成二次污染,除了存在于有机硫化物中, S―S键还存在于胱氨酸等蛋白质中, S―S键的形成和断裂决定该类蛋白质的活性.本工作中,我们研究了用实验室常见的Nd:YAG激光器的四倍频266 nm激光光解C2H5SSC2H5过程,通过激光诱导荧光(LIF)光谱方法检测乙硫自由基C2H5S等光解产物.实验表明266 nm激光主要光解C2H5SSC2H5的S―S键产生C2H5S自由基.本文应用密度泛函理论的Becke3-Lee-Yang-Parr泛函(B3LYP方法)得到C2H5SSC2H5的S―S键、C―S键和C―C键的解离势能曲线,可知在266 nm光解条件下, C2H5SSC2H5在基态能够发生S―S键、C―S键解离, C―C键不发生解离.本文采用全活化空间自洽场(CASSCF)方法优化得到态和态的C2H5S自由基结构及其跃迁的绝热激发能,以辅助解析实验检测的C2H5S自由基的LIF光谱.实验结合理论计算最终得出,本实验266 nm光解条件下, C2H5SSC2H5主要发生S―S键解离,不排除少量分子发生C―S键解离的可能性.  相似文献   

9.
本文用从头计算方法研究了含32个顶点的硼烷B32H322-及裸原子簇B32与C2B30的构型、稳定性及反应活性。B32的优化计算结果表明,12个5配位与20个6配位两类硼原子不在同一球面时最稳定,而且所含两种B-B核间距离(R56R66)的优化值验证了Lipscomb的经验数值。B32、B32H322-电子结构及原子布居的计算表明骨架成键轨道满足Wade规则。相应的计算还表明,中性BB32H32可能稳定存在,但构型的对称性将低于Ih对称,另外。对C2B30结合能的计算及前线轨道性质的分析表明,C2B30热稳定性较高,并且有较强的得电子反应活性。  相似文献   

10.
李炎 《应用化学》1985,(2):97-97
本文详尽地分析了推广的休克尔分子轨道理论方法(EHMO)中参量化过程。借助于计算双原子体系选择出合理的经验参数和近似方式,引进了过渡金属内层原子轨道排斥作用项。分别计算了H,H2,C2H4和C2H3在铂及铂锡合金上化学吸附键能,计算结果表明,同铂金属比较,在铂锡合金上H原子,C2H4分子的化学吸附键变弱在锡富集的铂锡合金上单个的铂原子不能解离吸附H2分子,在铂锡合金上C2H4脱氢反应较难进行。  相似文献   

11.
A state-specific scheme for time-dependent density functional theory (SS-TDDFT) based on the Davidson algorithm is presented. SS-TDDFT is a method devised for speeding up TDDFT calculations by screening transitions that contribute to a specific excitation. By applying this method to calculations of the low-lying excitation energies of test molecules (N2, CO, H2CO, C2H4 and C6H6), water clusters and polyenes, we found that SS-TDDFT accurately reproduced the excitation energies of standard TDDFT while drastically reducing the rank of the TDDFT response matrix without loss of accuracy. We have thus formulated TDDFT that works more efficiently and economically for memory storage.  相似文献   

12.
应用密度泛函B3LYP方法和从头算(abinitio)HF方法,在3-21G理论水平上,对具有C2v,D2d,D3h和D6h对称性的四种C36异构体以及在保持D2d,D3h和D6h对称性条件下形成的不同氢化物进行了量子化学计算,研究了它们在不同量子态时的分子几何构型和电子结构.结果表明,电子相关效应在C36簇化合物的电子结构中起着重要作用.它们最稳定的结构是C363A2u量子态D6h异构体,而C36的氢化物是在D3h异构体的C2位置等同碳原子上形成的1A1'量子态氢化物C36H12.  相似文献   

13.
Theoretical calculations (DFT, MP2) are reported for up to four sets of reaction products of trimethylphosphine, (CH3)3P, each with H2O, HCl and HF together with DFT calculations on up to three sets of reaction products of substituted phosphonium cations, (CH3)3P–R+. These products comprise (a) P(III) normal complexes (CH3)3PHY, (b) P(IV) ‘reverse’ complexes Y(H–CH2)3P–R, (c) P(IV) ylidic complexes YHCH2(CH3)2P–R and (d) P(V) covalent compounds Y–P(CH3)3–R for Y=HO, Cl and F and R=H, CH3, C2H5, C2H4OH and C2H4OC:OCH3. Calculations are carried out at the B3LYP/6-31+G(d,p) level in all cases and also at the MP2/6-31+G(d,p) level for systems in which R=H. Minimum energy structures are determined for predicted complexes or structures and geometrical properties, harmonic vibrations and BSSE corrected binding energies are reported and compared with the limited experimental information available. Potential energy scans predict equilibria between covalent trigonal bipyramidal P(V) forms and reverse complexes comprising hydrogen bonded or ion pair, tetrahedral P(IV) forms separated by low potential energy barriers. Similar scans are also reported for equilibria between reverse complexes and ylidic complexes for Y=OH and R=CH3, C2H5, C2H4OH and C2H4OC:OCH3. Corrected binding energies, structures and values of harmonic modes are discussed in relation to bonding The names ‘pholine’ and ‘acetylpholine’ are suggested for phosphorus analogues to choline and acetylcholine.  相似文献   

14.
The photophysical properties of a homologous series of 2, 4-6-triaryl pyrylium tetrafluoroborates substituted by six alkoxy chains (CnH2n+1O, n = 2, 3, 4, 5, 8, 12) are reported. in dilute solution, the electronic absorption and fluorescence spectra do not depend on the length of the alkoxy chains while both fluorescence lifetimes and fluorescence quantum yields increase when the chain length increases. Monomer and excimer fluorescence is observed with the pure compounds; the steady state and time resolved emission spectra and the decay kinetics which do not depend on the chain length suggest that the columnar structure exist with very short lateral chains. Excimer lifetimes determined in the liquid-crystalline phases follow an exponential law as a function of the reciprocal temperature: τ ∝ exp (EM/RT). The activation energy for excimer migration is 0.046 eV, 0.061 eV and 0.087 eV respectively for n = 5, 8 and 12.  相似文献   

15.
16.
The D1-D0 electronic spectrum of jet-cooled cyanocyclopentadienyl (C5H4CN) radical, produced by excimer laser photolysis of 1,3-cyclopentadiene-1-carbonitrile (C5H5CN), was measured by laser-induced fluorescence (LIF). The LIF spectrum was identical to that of radicals produced by photolysis of phenyl isocyanate and o-chloroaniline, which had been assigned to phenyl nitrene. This result shows that the nascent radical product in the photolysis of o-chloroaniline and phenyl isocyanate is isomerized to C5H5CN and the final product of C5H4CN radical is derived via the second photolysis. The rotational contour of the 0-0 band of the C54CN radical, at 27143 cm−1 (368.3 nm), is also presented. The electronic transition is A-type and π electron transition, and the symmetry of both the ground and excited electronic state is 2B1 (of the C2v point group).  相似文献   

17.
The redox characteristics of the ternary clathrate compound {Mo[S2CN(C2H5)2]4}+{C6H5CH2SSCH2C6H5}-was studied by electrochemical measurement and quantum-chemical calculations.The cyclic voltammogram of this ternary clathrate compound in 0.1M KClO4-DMF with a platinum electride had 2.pairs of redox peak.Both the electrochemical parameters derived from the voltammogram and the results of EHMO calculations indicate that the pair of redox peak at relatively positive potentials corresponds to the redox reaction of Fe(Ⅲ)/Fe(Ⅱ) which is irreversible in nature,while the pair of redox peak at more negative potentials corresponds to the redox reaction of Mo(Ⅴ)/ Mo(Ⅱ) which is semi-reversible.The calculations from experiment measurements are fairly agreement with the theoretical calculations.  相似文献   

18.
On the basis of ab initio MP2/6–31 + + G(2d,2p) calculations, we examined the potential energy surfaces of the water·hydrocarbon complexes H2O·CH4, H2O·C2H2 and H2O·C2H2 to locate all the minimum energy structures and estimate the hydrogen bond energies and vibrational frequencies associated with the C(spn)---H·O and the O---H·C(spn) bonds (n = 1−3). Our calculations show that H2O·C2H2, H2O·C2H4 and H2O·CH4 have two minimum energy structures (i.e., the C---H·O and O---H·C hydrogen bond forms), but H2O·C2H4 has only one when the vibrational motion is taken into account, the O---H·C hydrogen bond form. We have also computed the barrier for the interconversion from one minimum to the other. The fully optimized geometries of H2O·CH4, H2O·C2H4 and H2O·C2H2 as well as the vibrational shifts of the C---H stretching frequencies in their C---H·O hydrogen-bonded forms are in good agreement with the available experimental data. The calculated hydrogen bond energies show that the C(spn---H·O bond strengths decrease in the order C(sp)---H·O>C(sp2)---H·O>C(sp3)---O>C(sp3---H·O, which is also consistent with the available experimental data.  相似文献   

19.
《Liquid crystals》2000,27(6):801-812
Various substituted aminodiphenyldiacetylenes of the type with X = C3H7, C5H11, F or NO2 and R, R' = H, CH3-C6H13 were synthesized and their mesomorphic properties determined. Semi-empirical and ab initio quantum chemical calculations using AM1, 421G and 631G* suggested that the amino group would increase the dielectric anisotropy and optical birefringence as compared to the alkyl chain. Mesomorphic properties were found to be poor with the maximum nematic phase range being 44.8°C and many of the compounds having no nematic phase. Both melting temperatures and enthalpies for those having nematic phases were too high to form good eutectic mixtures.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号