小团簇Con（n=1~7）吸附O, CO, CO2的 密度泛函研究

ConA团簇;DFT;吸附;电子性质;CO氧化     

基于密度泛函理论的Bn（n=1-8）团簇结构和稳定性研究

采用密度泛函理论（DFT）中的B3LYP方法,在6—31G^＊水平上对Bn（n=2—8）团簇的各种可能的几何构型和电子结构进行了优化和振动频率计算,结果表明,Bn微团簇的稳定结构大部分为平面结构,只有极少数立体结构属于基态稳定结构。平面结构分为链状和环状结构两种,链状结构的所有原子均处于同一平面,且处于链状结构两端的键长稍短,原子向内部收缩。环状稳定结构均为一个n元环中心有一个配位的硼原子,通过对基态结构的平均原子结合能和能量二次差分的计算,得到n为奇数时团簇较为稳定。     

SrO分子在GaN(0001)表面吸附的密度泛函理论研究

建立了SrO/GaN(0001)2×2表面吸附模型,采用基于第一性原理的密度泛函理论平面波超软赝势方法对SrO分子的吸附生长进行了计算,详细研究了SrO分子在表面的吸附位置、吸附能及表面化学键特性。计算发现,SrO分子在GaN(0001)表面吸附不会发生分解,最稳定吸附位为Ga桥位,吸附能达到7.257~7.264 eV。通过电荷布居数和态密度分析,SrO分子吸附后O与表面的一个Ga原子形成的化学键表现出共价键特征,电子由SrO转移给表面部分Ga原子,GaN(0001)仍存在表面态。     

Ba2+在KDP(100)表面吸附的密度泛函理论研究

为了研究Ba~(2+)与KDP晶体表面相互作用的本质,采用密度泛函理论(DFT)方法对Ba~(2+)在KDP(100)表面的吸附行为进行计算。结果表明:Ba~(2+)在KDP(100)表面的吸附能为负值,吸附过程为自发的放热反应。通过结构优化得到3种稳定的吸附构型,最终吸附位置为O原子的顶位或两个O原子之间的桥位。当Ba~(2+)位于磷酸根基团中的两个O原子之间的桥位时,吸附最稳定。在3种吸附构型中,Ba~(2+)与表面O原子均通过离子键结合,而与表面最外层H原子则会产生一定的共价相互作用。另外,Ba~(2+)吸附使KDP(100)表面的P—O键、H—O键以及K—O键有不同程度的伸长或缩短,同时表面的氢键结构也发生了明显的变化。     

用密度泛函理论研究汞在CeO_2(111)表面的吸附

采用密度泛函理论计算了Hg、HgCl、HgCl_2在CeO_2(111)表面的吸附构型、吸附能和态密度。结果表明,Hg在CeO_2(111)表面属于弱化学吸附。HgCl与CeO_2(111)表面为强化学吸附,是反应的重要中间体。HgCl_2在CeO_2(111)表面是物理吸附,易发生解离,脱除。氯对于汞的吸附和氧化产生较强的影响,这与实验结果相一致。基于计算结果,得到汞在CeO_2(111)表面的反应机理。     

碳纳米管低温吸附储氢特性的密度泛函理论(DFT)研究

应用密度泛函理论（DFT）分析了与常温、高压储氢试验和计算机分子模拟有相同管结构参数碳纳米管的低温吸附储氢性能。理论计算包括定压下,管内密度分布与温度变化的关系,定温、定压下,纳米结构变化对密度分布的影响,碳纳米管可利用容积比率（UCR）与系统压力、温度的关系,典型管径碳纳米管的吸附等温线。计算结果显示了碳纳米管良好的低温吸附储氢潜力。     

掺杂和修饰的石墨烯对半胱氨酸吸附性能的密度泛函理论研究

使用密度泛函理论计算了掺杂或修饰Al或Mn原子的石墨烯对半胱氨酸的吸附性能。计算结果表明,掺杂或修饰Al或Mn原子后,Graphene与半胱氨酸之间结合稳定,具有较大的结合能。其中掺杂或修饰Mn原子的体系的吸附能整体高于掺杂或修饰Al原子的体系。石墨烯上修饰或掺杂Al或Mn原子,增加了石墨烯基底与半胱氨酸之间的电荷转移,特别是修饰方式显著改变了费米能级附近的性质,同时改变了Graphene的电导性质。Al或Mn原子修饰或者掺杂的Graphene除了增加对半胱氨酸吸附能力外,也是一种潜在的检测半胱氨酸的传感器材料,进而在生物领域得到更广泛的应用,比如用来检测富含半胱氨酸的金属硫蛋白。     

密度泛函理论研究贵金属耦合纳米团簇的静电极化率与吸收光谱

基于密度泛函理论计算了2个贵金属(Ag、Au、Cu)纳米团簇组成的团簇对的静电极化率和吸收光谱,结果表明这2个团簇之间存在强烈的静电耦合效应,其贡献主要来自于外加弱电场下团簇之间的电荷迁移和电子云的扭曲。随着团簇对间距的不断增大,静电极化率先增大后减小,存在一个极化率最大的最佳位置。在团簇对的吸收谱中,随着团簇对间距的增加,高能峰的位置和强度基本保持不变,而低能峰则不断蓝移且峰值先增大后减小,最终消失于高能峰的位置。进一步计算团簇-吡嗪和团簇-吡嗪-团簇体系的静电极化率和吸收光谱,结果发现团簇连接有机小分子后部分电子将从有机小分子向团簇迁移,使整个体系具有较大的固有极矩,在外加弱电场下,团簇与有机小分子之间的电荷迁移能力显著增强。     

团簇Co3FeP的成键方式与磁性

为研究非晶态合金Co-Fe-P体系的成键方式及磁性,在较高的量子化学水平下,利用密度泛函理论,以团簇Co₃FeP为局域模型展开研究,结果发现：团簇的自旋多重度和几何形态均会影响其成键杂化方式和磁性;团簇Co₃FeP中存在pd²、s²p²d³、p²d、p³d、p³、pd³杂化,其中Co-Fe键主要由Co3d和Fe3d、Co4p和Fe4p形成的d²和p²杂化组成;Co-P键主要是Co3d和P3p形成的pd杂化;Fe-P键主要是Fe3d和P3p形成的pd杂化。Co原子和Fe原子在提供磁性时,相互制衡。综合来看,d轨道对团簇Co₃FeP的成键方式和磁性有着重要影响。     

Geometric and Electronic Structures of Tc and Mn Clusters by Density Functional Calculations

The geometric structures of Tc₂-Tc₅ and Mn₂-Mn₈ clusters were optimized by the Amsterdam density functional method. The trimeric, tetrameric, and pentameric Tc clusters exhibit the equilibrium structures of isosceles triangle, tetrahedron, and square pyramid, respectively. The structures of the Mn clusters up to Mn₄ are similar to those of the respective Tc clusters, while the Mn₅, Mn₆, Mn₇, and Mn₈ clusters have the distorted trigonal bipyramidal, distorted octahedral, pentagonal bipyramidal, and C2v structures, respectively. The Tc clusters are paramagnetic, while the Mn clusters are basically ferromagnetic.     

Magnetic Properties of Oxygen Clusters

Magnetic properties of oxygen pair clusters are investigated theoretically for different geometries of clusters which can be realized by doping molecular cryomatrices with oxygen. Anomalous temperature and pressure behavior of the magnetic susceptibility, magnetic heat capacity and magnetic entropy is predicted. It is shown that the low-temperature magnetic susceptibility of these solid solutions is very sensitive to the orientational structure of impurity oxygen clusters, which makes it possible to use the susceptibility data for studying structural and dynamics properties of the host lattice, including high-pressure phases of simple molecular crystals.     

Monte Carlo Simulations of Structural and Thermodynamic Properties of Xe Clusters Adsorbed on Graphite

Atomic clusters from 7 up to 1300 Xe atoms adsorbed on a graphite surface have been studied using the Monte Carlo method. The interaction model includes all physically important terms. In particular, the interaction of Xe atoms with the substrate includes the corrugation energy with a periodicity that corresponds to the graphite 001 planes. Results show that the Xe layers are never uniformly incommensurate because locally they always try to accommodate their structure to the corrugation of the surface. The competition between the atom-atom and atom-surface interaction leads to modulated Xe layer structures with a local tendency to form registered areas.     

Density Functional Theory Study on the Oxidation of Hydrosilylated Silicon Nanocrystals

As a leading surface modification approach,hydrosilylation enables freestanding silicon nanocrystals(Si NCs) to be well dispersed in a desired medium.Although hydrosilylation-induced organic layers at the NC surface may somehow retard the oxidation of Si NCs,oxidation eventually occurs to Si NCs after relatively long time exposure to air.We now investigated the oxidation of hydrosilylated Si NCs in the frame work of density functional theory(DFT).Three oxygen configurations that may be introduced by the oxidation of a Si NC are considered.It is found that a hydrosilylated Si NC is less prone to oxidation than a fully H-passivated Si NC in the point of view of thermodynamics.At the ground state,backbond oxygen(BBO) and hydroxyl(OH) hardly change the gap between the highest occupied molecular orbital(HOMO) and the lowest unoccupied molecular orbital(LUMO) of a hydrosilylated Si NC.At the excited state,the decrease in the HOMO-LUMO gap induced by the introduction of doubly bonded oxygen(DBO) is more significant than that induced by the introduction of BBO or OH.We have correlated the changes in the optical absorption(emission) of a hydrosilylated Si NC after oxidation to those of the HOMO—LUMO gap at the ground state(excited state).     

有机小分子调控下的羟基磷灰石的合成

以甘氨酸和乙二胺为模型分子,在中性条件下采用水热法,研究有机小分子对羟基磷灰石(HAP)晶体生长形貌的影响。采用透射电子显微镜(TEM)、X射线衍射仪(XRD)和傅里叶变换红外光谱仪(FTIR)分析了合成产物的形貌、结构和组成。实验结果表明,甘氨酸诱导合成的HAP呈六方棒状,长500～2000nm,直径为50～100nm;在乙二胺的诱导下合成了长100～250nm、宽30～50nm的片状HAP晶体。对照空白实验可知,小分子上的极性基团通过静电吸附或分子占位显著影响HAP的形貌。     

Magnetic Properties and the Arrangement of Molecular Oxygen Adsorbed in the Microporous Coordination Polymer Cd(bpndc)(bpy)

The magnetic properties of O₂ adsorbed in the microporous coordination polymer Cd(bpndc)(bpy) were investigated by means of high-field magnetization measurement. The magnetization of adsorbed O₂ has a paramagnetic-like behavior in the low-field region and increases steeply above 50 T. The experiment results suggest that the half of adsorbed O₂ that forms O₂–O₂ dimer causes the metamagnetic-like behavior and the remaining O₂ causes paramagnetic-like behavior owing to nearly isolated spin. A possible arrangement of O₂ is suggested.