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The influence of position of the substitution, strength and number of donors and acceptors, and their coplanarity and asymmetry is discussed. The results indicate that the molecules may have larger first hyperpolarizabilities when the molecules have stronger and more donors and acceptors, large asymmetry of HOMO and LUMO, better coplanarity and higher accentricity. This work attemps at finding out the relationship between the structure and the property, thus providing theoretical basis for designing nonlinear optical molecules.

进一步研究体系中取代基的位置，给体与受体的数量和得失电子的能力，分子的共面性和对称性对分子第一超极化率的影响，结果表明，有机分子拥有更多数量与更强得失电子能力的给体和受体，最高占据分子轨道和最低未占据分子轨道空间分布的不对称，具有较高的原子共面性和较低的分子中心对称性，都能显著增加

At the normal state, porphyrin molecules do not have EPR signal. However, light excitation may cause a transition of porphyrin molecules from singlet to triplet. At the same time, the change from diamagnetism to paramagnetism occurred to porphyrin molecules. In this case, the two un-paired electrons are nearby each other and cause a strong interaction, giving EPH signal with sharp peak at g = 2.000. The g value increased with an increase in electron cloud density.

常态下卟啉分子没有EPR信号，在光的激发下，卟啉分子由原来的逆磁性分子变成顺磁性的激发三重态分子，这种激发三重态分子在分子轨道上具有两个未成对电子，这两个电子相距很近，彼此之间发生很强的相互作用而产生电子，它的g值随卟啉共轭体系平均电子云密度增大而变大。

At the normal state, porphyrin molecules do not have EPR signal. However, light excitation may cause a transition of porphyrin molecules from singlet to triplet. At the same time, the change from diamagnetism to paramagnetism occurred to porphyrin molecules. In this case, the two un-paired electrons are nearby each other and cause a strong interaction, giving EPR signal with sharp peak at g =2.000. The g value increased with an increase in electron cloud density.

常态下卟啉分子没有EPR信号，在光的激发下，卟啉分子由原来的逆磁性分子变成顺磁性的激发三重态分子，这种激发三重态分子在分子轨道上具有两个未成对电子，这两个电子相距很近，彼此之间发生很强的相互作用而产生电子，它的 g 值随卟啉共轭体系平均电子云密度增大而变大。

The process of dip pen lithography involves the adsorption of ink molecules on AFM tip ,the formation of water meniscus ,the transport of ink molecules ,and diffusion of ink molecules on the substrate .More factors such as temperature ,humidity ,tip ,scanning speed and so on will influence the process of dip pen lithography .

蘸水笔技术的刻蚀过程包括AFM 针尖对墨水分子的吸附、针尖与基底间弯月液桥的形成、墨水分子在液桥中的传输、墨水分子在基底的扩散等四个阶段，并受温度、湿度、针尖、扫描速度等多种因素的影响。

Since most of the large molecules containing phosphorus element have double bonds, it is necessary to consider the special structures of double bonds in order to deal with these large systems more accurately. So, based on density functional theory and electronegativity equalization principle, applying a general atom-bond electronegativity equalization method , using separated program, through regression and least-squares optimization , the parameters of atoms and bonds in molecules are determined . By these parameters , the charge distributions and the energy of some molecules containing phosphorus element, especial the fragment of DNA, RNA, are calculated . The results are quite good.

由于这些含磷生物大分子体系都含有双键，为了明确的处理双键，进而更准确的解释带有双键和共轭双键的含磷生物大分子结构与性质的关系，我们以密度泛函理论~([1-4])和电负性均衡原理~([5-9])为基础，应用和开发原子-键电负性均衡方法中的σπ模型，利用最小二乘法，拟合确定了一些分子（含碳、氮、氧、氢以及磷等原子）的各种类型原子及化学键区域的参数，并利用上述参数计算了一些多聚核苷酸的电荷分布以及分子的总能量，进行了讨论，得到的结果可以和从头算相媲美。

In this thesis, we focus on the theory for the interaction of molecular dipole moment with external electric field and use the numerical simulation to investigate the rotational state-selection of polar molecules in a hexapole electric field and the laser-field role of alignment or orientation for molecules based on semi-classical treatment, the detail is the numerical calculation for a quantum mechanical treatment of molecules and their interaction with the external field and a classical electrodynamical treatment for static electric field.

本文研究是在描述分子偶极矩（永久偶极矩或诱导偶极矩）和外电场相互作用的基础上，我们建立了对分子态选择和角动量取向、准直研究的半经典理论框架（即分子体系状态、能量及与外场相互作用使用量子理论描述，分子的运动轨迹使用经典电动力学描述），并利用数值计算方法对静电场和随时间变化电场作用下分子的转动态选择、取向和准直过程进行了研究。

The results show that the ECM potential behaves well in whole internuclear region, and that the ECM not only gives satisfied potentials for smaller diatomic molecules but also generates correct potential energies for heavier molecules like halogen diatomic molecules.

研究表明，ECM势不仅有优秀的物理性质，而且在分子振动全程具有较高的精度；ECM不仅能给出小分子电子态的满意势能结果，而且对于其电子构造和物理及化学性质都有一定特殊性的卤素双原子分子，也同样能给出正确的势能曲线。

Polyatomic molecules Compared with diatomic and triatomic molecules and large clusters, the interaction of polyatomic molecules with intense femtosecond laser field need to be paid more attention.

多原子分子相对于简单的小分子和团簇分子而言，多原子分子与强激光的相互作用还缺少深入的研究。

The "best" way to solvate a system is to place explicit water molecules in the simulation box with the molecules of interest and treat the water molecules as interacting particles like those in the molecule.

为体系添加溶剂的最好的途径是在模拟盒子中添加明确的水分子。

There are two independent molecules of ZnL or Co(IIL and two water molecules in one asymmetric unit of complex 1(or 2), the crystal structure of CuClL1·2H2O consists of one molecule of CuClL1 and two water solvate molecules in the asymmetric unit, while the ZnL·CH3OH (4) comprises of one molecule of ZnL and a methanol molecule in per unit.

在这四个金属配合物中，配合物(1)和配合物(2)的每个不对称单元中有两个独立的ML 分子和两个水分子，配合物(3)的每个不对称单元中有一个CuClL1分子和两个水分子，而配合物(4)的每个不对称单元中只有一个ZnL 分子和一个甲醇分子。

The split between the two groups can hardly be papered over.

这两个团体间的分歧难以掩饰。

This approach not only encourages a greater number of responses, but minimizes the likelihood of stale groupthink.

这种做法不仅鼓励了更多的反应，而且减少跟风的可能性。