硝酸乙酯分子间相互作用的ab initio研究

在abinitio-HF/6-31G水平上求得硝酸乙酯二聚体势能面上的四种优化构型和电子结构。经MP2电子相关校正和基组叠加误差(BSSE)以及零点能(ZPE)校正，求得二聚体的最大结合能为11.46kJ.mol^-^1，还进行HF/6-311G和HF/6-311++G水平的总能量比较计算，发现6-31G基组对计算结合能比较适合，二子体系间的电荷转移很少，对优化构型进行振动分析，并基于统计热力学求得从单体形成二聚体的热力学性质变化。     

NTO二聚体分子间相互作用的理论研究

在DFT-B3LYP/6-311＋＋G**水平上求得NTO二聚体势能面上六种优化构型和电子结构. 经基组叠加误差(BSSE)和零点能(ZPE)校正, 求得分子间最大相互作用能为－53.66 kJ/mol. 二子体系间的电荷转移很少. 由自然键轨道分析揭示了相互作用的本质. 对优化构型进行振动分析, 并基于统计热力学求得200.0～800.0 K温度范围从单体形成二聚体的热力学性质变化. 发现二聚主要由强氢键所贡献, 但结合能大小并不为氢键所完全决定. 二聚过程在较低温度或常温下能自发进行.     

1H-ANTA二聚体分子间相互作用的密度泛函理论研究

在DFT-B3LYP/6-311＋＋G**水平上求得1H-3-硝基-5-氨基-1,2,4-三唑(1H-ANTA)二聚体势能面上5种优化构型和电子结构. 经基组叠加误差(BSSE)和零点能(ZPE)校正, 求得分子间最大结合能为70.63 kJ/mol. 二聚体的形成使电荷向三唑环转移. 由氢键强弱推断二聚体稳定性的顺序与结合能顺序相一致, 氢键是二聚体的主要作用形式. 对优化构型进行振动分析, 并基于统计热力学求得200.0～800.0 K温度范围内单体形成二聚体的热力学性质变化. 发现在该温度范围所有二聚过程均能自发进行.     

2,3,7,8-四氯苯并二英分子结构与热力学性质的理论研究

用密度泛函理论(DFT)和从头算(ab initio)方法,在B3LYP/6-31G、 B3LYP/6-31G*、 B3LYP/6-311G*和MP2/6-31G*水平上全优化计算了2,3,7,8-四氯苯并二英(2,3,7,8-TCDD)的几何构型、电子结构和振动频率,并用校正后的频率计算了298～1500 K的标准热力学函数,同时用半经验的PM3 SCF-MO进行了同样的计算,计算结果与实验值及文献值较好地吻合.     

N-甲硝胺二聚体分子间相互作用的理论研究

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。     

α-双环-HMX晶体中二聚作用的理论研究

在四种(分别为HF/6-31G*,MP2/6-31G*,B3LYP/6-31G*和PBE1PBE/6-31G*)水平下,用超分子方法(SM)求得α-双环-HMX(四硝基四氮杂双环辛烷)三种二聚体(I,II和III)中的分子间相互作用能.用对称性匹配微扰理论(SAPT)与密度泛函理论(DFT)相结合的方法[SAPT(DFT)方法]求得该三种二聚体的分子间相互作用能及其分量.在四种SM方法中,以MP2求得的相互作用最强,但均弱于SAPT(DFT)的计算结果.SM和SAPT(DFT)两种方法求得的相互作用,均为IIIIII,归因于三者的分子质心平衡间距(Re)6.58(I)6.95(III)8.60(II).考察SAPT(DFT)方法求得的各作用能分量是IIIIII.密度泛函方法对色散能计算的丢失使其求得的相互作用偏小.     

硝酸甲与硝酸乙酯的结构、振动频率和热力学性质的密度函数 理论(DFT)研究

用密度函数理论(DFT)的BLYP和B3LYP方法,取6-31G,6-31G^*,6-31G^*^*,6-311G,6-311G^*和6-311G^*^*六种基组,对硝酸甲酯和硝酸乙酯的几何构型和红外振动频率进行了计算研究.结果表明,B3LYP方法在采用极化基组(6-31G^*,6-31G^*^*,6-311G^*和6-311G^*^*)时计算得到的结果均较好,适用于硝酸酯类化合物的研究.而BLYP方法无论采用何种基组均不适用;运用校正后的B3LYP/6-31G^*频率(校正因子0.975)计算得到的热力学性质(C^o~p,H^o和S^o)与实验结果较吻合。     

硝酸甲与硝酸乙酯的结构、振动频率和热力学性质的密度函数 理论(DFT)研究

用密度函数理论(DFT)的BLYP和B3LYP方法,取6-31G,6-31G^*,6-31G^*^*,6-311G,6-311G^*和6-311G^*^*六种基组,对硝酸甲酯和硝酸乙酯的几何构型和红外振动频率进行了计算研究.结果表明,B3LYP方法在采用极化基组(6-31G^*,6-31G^*^*,6-311G^*和6-311G^*^*)时计算得到的结果均较好,适用于硝酸酯类化合物的研究.而BLYP方法无论采用何种基组均不适用;运用校正后的B3LYP/6-31G^*频率(校正因子0.975)计算得到的热力学性质(C^o~p,H^o和S^o)与实验结果较吻合。     

量子化学研究水对Adenine-Thymine碱基对构型的影响

利用Hartree-Fock方法, 选取6-31G*基组对Adenine-Thymine-Water氢键复合物可能存在的构型进行了优化, 然后用DFT PBE方法, 选取6-311＋＋G(3d, 3p)基组对复合物的结合能进行计算, 结果表明水与DNA中配对碱基的相互作用, 不会显著影响碱基对的稳定性, 水的存在使得碱基对的扭转构型更接近真实DNA中碱基对的螺旋状结构.     

6-烷基鸟嘌呤与DNA碱基间氢键作用的理论研究

用密度泛函B3LYP方法在6-311＋G**基组水平上对鸟嘌呤及顺(cis-)、反式(anti-)-6-烷基鸟嘌呤(O⁶-AlkylG)与DNA碱基(胸腺嘧啶T、胞嘧啶C、腺嘌呤A、鸟嘌呤G)的氢键二聚体结构进行了优化. 在MP2/cc-pVXZ(X＝D,T)// B3LYP/6-311＋G**水平上, 采用完全基组外推方法校正了氢键二聚体的相互作用能, 并用完全均衡校正法(CP)校正了基组重叠误差(BSSE). 在B3LYP/6-311＋G**水平上计算了各氢键碱基对的全电子波函数, 并用分子中的原子理论(AIM)分析了碱基间的弱相互作用. 计算结果显示, 鸟嘌呤6-O烷基化改变了碱基间的氢键作用模式, 使碱基对发生了明显的螺旋桨式扭转和不同程度的位移, 碱基间的电子密度分布和氢键作用能明显减小. O⁶-AlkylG对DNA碱基间的氢键作用是去稳定化的, 去稳定化影响的顺序为GC＞GG＞GA≈GT. 计算结果与文献给出的实验结论基本一致.     

Pi-pi interaction in pyridine

pi-pi Interaction in pyridine dimer and trimer has been investigated in different geometries and orientations at the ab initio (HF, MP2) and DFT (B3LYP) levels of theory using various basis sets (6-31G, 6-31G, 6-311++G) and corrected for basis set superposition error (BSSE). While the HF and DFT calculations show the pyridine dimer and the trimer to be unstable with respect to the monomer, the MP2 calculations show them to be clearly stable, thus emphasizing the need to include electron correlation while determining stacking interaction in such systems. The calculated MP2/6-311++G binding energy (100% BSSE corrected) of the parallel-sandwich, antiparallel-sandwich, parallel-displaced, antiparallel-displaced, T-up and T-down geometries for pyridine dimer are 1.53, 3.05, 2.39, 3.97, 1.91, 1.47 kcal/mol, respectively. The results show the antiparallel-displaced geometry to be the most stable. The binding energies for the trimer in parallel-sandwich, antiparallel-sandwich, and antiparallel-displaced geometry are found to be 3.18, 6.14, and 8.04 kcal/mol, respectively.     

F原子与臭氧反应机理的量子化学研究

用量子化学从头计算UMP2方法，在UPM2/6 311＋G水平上，研究F 原子与臭氧反应机理，优化了反应物、产物、中间体和过渡态的几何构型，在UQCISD（T）/6 311＋G水平上计算能量，同时进行零点能校正.研究结果表明， F原子与臭氧之间有很强的反应活性.     

Theoretical Study on Intermolecular Interactions and Thermodynamic Properties of Nitroamine Dimers

Ab initio self-consistent field(SCF) and Mφller-Plesset correlation correction methods employing 6-31G^** basis set have been applied to the optimizations of nitroamine dimers.The binding energies have been corrected for the basis set superposition error (BSSE) and the zero-point energy.Theree optimized dimers have been obtained.The BSSE corrected binding energy of the most stable dimer is predicted to be -31.85kJ/mol at the MP4/6-31G^**//MP2/6-31G^** level.The energy barriers of the Walden conversion for -NH2 group are 19.7kJ/mol and 18.3kJ/mol for monomer and the most stable dimer,respectively.The molecular interaction makes the internal rotation around N1-N2 even more difficult.The thermodynamic properties of nitroamine and its dimers at different temperatures have been calculated on the basis of vibrational analyses.The change of the Gibbs free energy for the aggregation from monomer to the most stable dimer at standard pressure and 298.2 K is predicted to be 14.05kJ/mol.     

ANTA的结构、性质及其互变异构的理论研究

对3-硝基-5-氨基-1,2,4-三唑(ANTA)的三种异构体,1H-ANTA(Ⅰ),2－ANTA(Ⅱ)和4H-ANTA(Ⅲ)在,bainitio-HF/3-21G和DFT-B3LYP/3-21G势能面计算的基础上,进行6-311G^**几何参数全优化,MP2总能量和SCRF溶剂(四氢呋喃)效应计算。以振动分析和统计热力学为基础,作标题物热力学性质以及Ⅰ和Ⅱ之间的互变异构反应计算,求得分子几何,电子结构和300～1000K范围的焓、熵和热容以及Ⅰ和Ⅱ互变异构平衡常数和速率常数。发现在三种异构体中在通常温度下以Ⅱ在气相下最稳定,Ⅰ在溶液中最稳定。低温下难以发生异构化反应,温度可提高Ⅰ与Ⅱ之间的互变速率,在800K时两种异构体在气相中等量共存;大于800K时Ⅰ更为稳定。     

丁二酰亚胺的结构、振动频率和热力学性质计算

用密度泛函理论（ＤＦＴ）和从头计算（ａｂ ｉｎｉｔｉｏ）方法,在Ｂ３ＬＹＰ／６－３１Ｇ、Ｂ３ＬＹＰ／６－３１１Ｇ和ＭＰ２／６－３１１Ｇ水平上,全优化计算了了二酰亚胺的分子几何构型和电子结构．进行了简正振动频率分析并用校正后的频率计算了２００－６００Ｋ温度范围的标准热力学函数,对计算结果进行了比较和讨论．     

Density functional theory study on molecular structure and vibrational IR spectra of isocytosine

Density functional theory with the combined Becke3-LYP exchange-correlation energy functional [DFT(B3-LYP) method] using the 6-31G(d, p) basis set is applied to predict molecular parameters (geometries, rotational constants, dipole moments) and vibrational IR spectra (harmonic wavenumbers, absolute intensities) of six tautomers of the isocytosine molecule. The results are compared with the corresponding data calculated at the conventional ab initio Hartree-Fock (HF) level using the same basis set and with available experimental data. Calculations show that (a) three amino tautomers are slightly nonplanar species with, evidently, a distorted amino group, (b) the DFT (B3-LYP)/6-31G(d, p) method predicts better molecular parameters, than do the HF calculations, and (c) the DFT(B3-LYP)-calculated vibrational IR spectra of isocytosine agree well with the available recorded IR spectra, and they show marked improvement over the IR spectra predicted at the HF/6-31G(d, p) level. Tautomeric stabilities of isocytosine are discussed on the basis of computed electronic energies by the DFT(B3-LYP) and ab initio approaches [including the MP2 and MP4(SDQ) calculations of electronic energies] and predicted zero-point vibrational energies by DFT(B3-LYP) and HF methods. This relative energies at 0 K of the tautomeric forms of isocytosine predicted by both conventional ab initio and DFT(B3-LYP) methods correlate well with the experimental data, showing the predominance of the aminohydroxy tautomer of isocytosine for an isolated molecule. © 1997 John Wiley & Sons, Inc.     

Spectroscopic and quantum chemical studies on 4-acryloyl morpholine

Fourier transform infrared (FTIR) and FT-Raman spectra have been recorded and an extensive spectroscopic investigations have been carried out on 4-acryloyl morpholine (4AM). Theoretical quantum chemical studies have also been performed. From the ab initio and DFT analysis using HF, B3LYP and B3PW91 methods with 6-31G(d,p) and 6-311G++(d,p) basis sets the energies, structural, thermodynamical and vibrational characteristics of the compound were determined. The energy difference between the chair equatorial and chair axial conformers of 4AM have been calculated by density functional theory (DFT) method. The optimized geometrical parameters, theoretical wavenumbers and thermodynamic properties of the molecule are compared with the experimental values. The effect of acryloyl group on the characteristic frequencies of the morpholine ring has been analysed. The mixing of the fundamental modes with the help of potential energy distribution (PED) through normal co-ordinate analysis has been discussed.     

Theoretical study on intermolecular interaction of epoxyethane dimer

Ab initio calculations at Hartree–Fock and fourth‐order Mø ller–Plesset (MP4) correlation correction levels with 6‐31G* basis set have been performed on the epoxyethane dimer. Dimer binding energies have been corrected for the basis set superposition error (BSSE) and the zero‐point energy. The greatest corrected dimer binding energy is −8.36 kJ/mol at the MP4/6‐31G*//HF/6‐31G* level. The natural bond orbital analysis has been performed to trace the origin of the weak interactions that stabilize dimer. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 78: 94–98, 2000     

A combined experimental and theoretical quantum chemical studies on 4-morpholinecarboxaldehyde

Extensive spectroscopic investigations have been carried out by recording the Fourier transform infrared (FTIR) and FT-Raman spectra and carrying out the theoretical quantum chemical studies on 4-morpholinecarboxaldehyde (4MC). From the ab initio and DFT analysis using HF, B3LYP and B3PW91 methods with 6-31G(d,p) and 6-311G++(d,p) basis sets the energies, structural, thermodynamical and vibrational characteristics of the compound were determined. The energy difference between the chair equatorial and chair axial conformers of 4MC have been calculated by density functional theory (DFT) method. The optimised geometrical parameters, theoretical wavenumbers and thermodynamic properties of the molecule were compared with the experimental values. The effect of carbonyl group on the characteristic frequencies of the morpholine ring has been analysed. The mixing of the fundamental modes with the help of potential energy distribution (PED) through normal co-ordinate analysis has been discussed.