采用密度泛函B3LYP方法，对水溶液中四面体配合物[Zn （NH3）m（H2O）n]2＋（m＋n＝4）结构和性质进行研究。在优化几何构型基础上，计算其最稳定构象的结合能及振动频率。结果表明：随着H2 O逐渐被NH3取代，配合物中的Zn2＋电荷主要转移到取代H2 O的NH3中的H上；Zn-O键和Zn-N键的键长逐渐增加，Zn-O键长始终大于Zn-N键长；随着m增大，配合物结合能变大；NH3数目的增加将导致Zn-O和Zn-N振动向低频方向移动，而O-H键和N-H键的各种振动谱线则会缓慢蓝移。

The 4-coordinate complexes [Zn (NH3)m(H2O)n]2+(m+n=4) in aqueous solution were in-vestigated by density function theory calculations ( B3 LYP functional ) .The geometries for the complexes were opti-mized to obtain the lowest-energy structures , of which the binding energies and vibrational frequencies were then calculated .The results show that the charge of zinc ions is mainly transferred to the hydrogen atoms of ammonia molecules which have taken the place of water molecules .The Zn-O bond length and Zn-N bond length increase gradually when water molecules are replaced by ammonia molecules , and the Zn-O bond is always longer than the Zn-N bond.With the increase of m, the binding energy of complexes becomes larger .As the number of ammonia molecules increases , the vibration of Zn-O and Zn-N bonds trends to lower frequencies .Meanwhile , the vibrational spectra of O-H bond and N-H bond will have a little blue-shift.

碱基是遗传物质DNA和RNA的基本结构单元，与基因突变、癌症及遗传疾病许多健康问题息息相关．使用MELD精密从头计算及自编程序，计算了常见碱基分子腺嘌呤、鸟嘌呤、胸腺嘧啶、胞嘧啶和尿嘧啶中沿各化学键方向上的单电子作用势，并根据单电子作用势势垒——D加对各化学键的强弱进行了比较．结果表明，N—H键的D加值明显高于C—H键的D坤值，且胸腺嘧啶分子的C7-H键的Dpb相对于其他分子的C—H键明显偏低．由于D曲可以用来表征化学键的强弱，因此，碱基分子中N—H键要强于C—H键，且胸腺嘧啶中的C7-H键最弱，在DNA中易被自由基或其他基团进攻，该结论与实验结果一致，为进一步探讨碱基分子的相关性质奠定了基础．

Nucleobases are the most important components of the genetic materials DNA and RNA , and may contribute to a variety of health-related problems including mutagenesis ,carcinogenesis and inherited disease .In this paper ,the potential energy barrier along all the C- H and N- H bonds for some familiar bases ,including adenine ,guanine ,thymine ,cytosine and uracil ,have been calculated by using the MELD ab initio method and our own program ,denoted by Dpb .The results showed that the N- H Dpb values are higher than the C-H Dpb values of all these nucleobases ,and the Dpb of C7-H bond in thymine is the lowest .Dpb is a new indicator for charactering the strength of the chemical bond .As a result ,the N-H bonds are stronger than the C- H bonds in all these molecules ,and the C7-H bond of thymine should be also a sensitive site for DNA damage with the lowest Dpb value . The results are in agreement with the experimental results .This work provides a new tool for explo-ring the properties fo

本文采用作者建立的分子内坐标下反应途径的动力学性质理论对HOD与H的选键反应进行了研究.以无选键性的HOH与H的反应和有选态性的H2(v=0,1)与OH的反应为对比,分别给出了每个反应内坐标下的垂直于IRC的振动模式的振动频率(ωK)及断裂键的振动模式与其它振动模式之间的耦合常数(BKL).通过它们对各反应选键性的分析,给出了在一定电子态下,为了达到选键反应的目的,该反应的断裂键振动频率和它与自身分子内其它键(键角)的耦合常数在理论上的要求.

The bond-selective reaction HOD and H has been studied with the theory of dynamical properties on reaction path (IRC) in molectular internal coordinates constructed by authors. Compared with the reaction HOH and H that has no bond selectivity and the reaction H2(υ=0,1) and OH that has mode selectivety, ωK (frequencies orthogonal to IRC) and BKL (coupling constants between breaking bond and the other vibrations ) of every reaction in internal coordinates have been obtained. In order to each the object of bond-selective reaction at certain electron state, the theoretic demands including the vibration frequencies ωK of breaking bond and the coupling constants BKL between breaking bond and the vibrations of other bond(bond angle) in the molecules have been obtained, based on the analysis of bond selectivity on each reaction.

为了研究FeAl金属间化合物的脆性，采用第一性原理计算方法，建立了FeAl超晶胞模型，对H原子掺杂前后的FeAl的电子结构进行计算。计算结果显示：在B2型金属间化合物FeAl中，Al原子的sp杂化轨道具有较强的方向性，参与形成的FeAl之间pd极化键导致了晶体的脆性。在H原子掺杂浓度为1.82%的情况下，FeAl体系中置入H原子，与H原子近邻的Al原子状态发生改变，更多的晶格电子为了与H原子成键，转化为共价电子，使晶体内局域金属性下降。由于H原子参与成键，晶体内形成具有明显各向异性的键络，更易于解理。

In order to study the brittleness of the FeAl intermetallic compounds, the first-principle calculation is adopted, a supercell FeAl model is establishing for calculating the electronic structure of FeAl before and after doping H atom. The calculation results show that: in the B2 type FeAl intermetallic compounds, the sp hybrid orbital of Al atoms has a strong directivity and the pd polarization bond participating in the formation of FeAl causes the brittleness of the crystal. When the doping concentration of H atoms is 1.82%, the H atoms is put into the FeAl system and then the state of Al atom will change which is near H atoms; more lattice electrons translate into shared electron to bond with H atoms, and make the metallicity descend at part of the crystal. Since the H atoms participate in the bonding, the bond network with obvious anisotropy forms in the crystal, which makes the cleavage be more easily.

对金属多重键配合物Cp2M2(μ-B4N4H8)(M=V,Cr,Mn,Fe)的结构和成键进行了理论研究,并与Cp2M2(μ-C8H8)进行对比.计算结果表明,在Cp2M2(μ-B4N4H8)基态构型中,B4N4H8配体均以硼为桥原子,金属原子的配位数均为5.其中,Cp2M2(μ-B4N4H8)(M=V,Cr,Mn)基态的结构和成键都与Cp2M2(μ-C8H8)非常接近;而Cp2Fe2(μ-B4N4H8)基态结构与Fe为4配位的Cp2Fe2(μ-C8H8)有所不同.Cp2M2(μ-B4N4H8)(M=V,Cr,Mn,Fe)基态结构分别为含V-V三重键的三态、含Cr-Cr三重键的单态、含Mn-Mn双键的三态及含Fe-Fe单键的单态.

The geometry and bonding of metal-metal multiple bond complexes Cp2 M2 (μ-B4 N4 H8 ) ( M=V, Cr, Mn, Fe) were theoretically investigated and compared with Cp2 M2(μ-C8 H8 ) . The calculated results show that in the ground states of Cp2 M2 (μ-B4 N4 H8 ) , the ligands B4 N4 H8 are all with B bridging atoms, the coordination numbers of M atom are all five. Among them, the structure and bonding of ground state of Cp2 M2(μ-B4 N4 H8 ) ( M = V, Cr, Mn ) are very close to Cp2 M2 (μ-C8 H8 ); while the ground state of Cp2 Fe2(μ-B4 N4 H8 ) is different with Cp2 Fe2 (μ-C8 H8 ) containing four-coordinated Fe. The ground-states of Cp2 M2(μ-B4 N4 H8 ) ( M=V, Cr, Mn, Fe) are respectively triplet state with V-V triple bond, singlet state with Cr-Cr triple bond, triplet state with Mn-Mn double bond, and singlet state with Fe-Fe single bond.