混合价聚十五钒酸盐[V_(15)O_(36)Cl](NH_4)_3Na_7·30H_2O的合成与晶体结构

以XRD法确定制得的标题晶体属空间群D_(3A)~3,a=13.111,c=11.130。结构由帕特逊-极小函数法结合差值法解出,经精修得一致性因子R_w=0.0344。晶胞中坐落在6m2特殊位置上的是包合1个Cl~-的聚十五钒酸根[V_(15)O_(36)Cl]~(10-),配合键价法确认这是四价钒占主导地位的一类特种混合价同多酸根。     

Optical properties of several ternary nanostructures

To investigate the optical properties of the ternary nanostructures, the nanodisk, core–shell, and three-sphere structures are constructed. The extinction coefficients and electric near-field distributions of these structures are calculated by the discrete dipole approximation(DDA) method. The result shows that the nanodisk structure has the best extinction efficiency in the three structures. Furthermore, several three-material combinations of the nanodisk structures are investigated. The ternary nanodisk structure composed of TiO₂ and two noble metals(Au, Ag or Pt) has higher extinction coefficient and near-field intensity than the nanodisk consisting of Au, TiO₂ and a semiconductor(Pb Se, Ge, MoS2, CdSe, CdS or TiO₂).Especially, TiO₂/Ag/Pt has the best extinction efficiency and the max electric near-field intensity. And the extinction spectra of TiO₂/Ag/Pt and TiO₂/Ag/Au structures are complementary in the visible range. This work conduces to the further research into ternary nanostructure and provides essential information about its performance in visible range.     

碱金属钠原子修饰硅原子团簇的结构及储氢性能研究

提出碱金属钠原子修饰笼形Si_6团簇的结构模型,采用密度泛函理论(DFT)研究钠原子修饰笼形Si_6团簇的结构及储氢性能.研究结果表明,氢分子与笼形Si_6团簇表面相互作用很弱,氢分子在其表面容易脱附.采用钠原子修饰笼形Si_6团簇后可有效避免氢分子的脱附,并且钠原子在笼形Si_6团簇的表面不发生团聚,有利于氢分子在其表面吸附和循环利用.研究发现在两个钠原子修饰笼形Si_6团簇的结构中,每个钠原子可以有效吸附六个氢分子.计算得到Na2Si_6团簇结构储氢的质量分数高达10.08 wt%,且氢分子的平均吸附能约为0.837 kcal/mol.可见,实现钠原子修饰笼形Si_6团簇结构在常温常压条件下储氢是有可能的.     

锂原子修饰硼原子链团簇的结构和储氢性能研究

采用密度泛函方法对锂原子修饰线型硼原子链团簇Li_2B_n(n=2~8)的结构及其储氢性能进行理论研究.结果显示,Li原子可键合于硼链团簇的两端,氢能以分子形式吸附在Li原子周围,每一个Li原子最多可吸附4个氢分子,氢分子的平均吸附能为2.020~2.832 kcal.mol~(-1).其中Li原子修饰B2小团簇的质量储氢分数最大,为31.24 wt%,表明在常温常压条件下它有可能成为一种潜在的储氢媒介.     

Diffusion and thermite reaction process of film-honeycomb Al/NiO nanothermite:Molecular dynamics simulations using ReaxFF reactive force field

The diffusion and thermite reaction process of Al/NiO nanothermite composed of Al nanofilm and NiO nano honeycomb are investigated by molecular dynamics simulations in combination with the Reax FF. The diffusion and thermite reaction are characterized by measuring energy release, adiabatic reaction temperature, and activation energy. Based on time evolution of atomic configuration and mean square displacement, the initialization of the thermite reaction process of Al/NiO nanothermite results from the diffusion of Al atoms. Under the microcanonical ensemble, it is found that the adiabatic reaction temperature of the thermite reaction process of Al/NiO nanothermite reaches over 5500 K, and activation energy is 8.43 k J/mol. The release energy of the thermite reaction process of Al/NiO nanothermite is 2.2 k J/g, which is in accordance with the available experimental value. With the same initial temperature, the adiabatic reaction temperature of the thermite reaction process of Al/NiO nanothermite has a tendency to decrease dramatically as the equivalence ratio increases. On the basis of chemical bond analysis, the initial temperature and equivalence ratio have great effects on the thermite reaction process, but do not significantly affect the average length of Al–Ni nor Al–O bond. Overall, the thermite reaction of film-honeycomb Al/NiO nanothermite is a complicated process instead of a theoretical equation.     

Li原子修饰笼型Si_6团簇的结构和储氢性能

利用杂化密度泛函B3LYP方法,在6-311+G(d,p)基组水平上对Si_6和Li修饰的Si_6团簇的几何结构和电子性质及储氢性能进行模拟计算和理论研究.结果表明,Si_6团簇最低能量构型为笼型结构,纯Si_6团簇不能有效吸附氢分子.Li原子的引入显著改善了Si_6团簇的储氢能力.以两个Li原子端位修饰Si_6团簇为载体,其氢分子的平均吸附能为1.692~2.755 kcal/mol,每个Li原子周围可以有效吸附五个氢分子,储氢密度可达9.952 wt%.合适的吸附能和较高储氢密度表明Li修饰Si_6团簇有望成为理想的储氢材料.