(Pt_nMn)^(±,0)(n=1～5)掺杂团簇结构与磁性的密度泛函研究

采用密度泛函理论(Density Function Theory)中的B3LYP方法,在Lanl2dz赝势基组水平上对(PtnMn)±,0(n=1~5)团簇的几何构型进行了全优化,并对基态的能级以及磁性进行了研究.结果表明:PtMn掺杂团簇的自旋多重度比较高,这种性质跟纯Mn团簇相似.并且发现一般情况下Mn原子参与成键数越多,结构越稳定,在成键数相同的情况下,成键的平均键长越短越稳定;其次(PtnMn)±,0团簇的所有稳定结构都表现为铁磁性耦合;掺杂一个Mn原子后的团簇磁性大大增强,磁矩主要来源于未满的d壳层电子,且Mn原子上的局域磁矩远大于Pt原子.随着Pt原子个数的增加,Mn原子的局域磁矩变化不大,但团簇的总磁矩渐渐增大.

Microstructure of NiSO4 Solution: A Combined DFT and EXAFS Study

The microhydration structure of nickel sulfate aqueous solution has been determined via density functional theory (DFT) calculation and extended X-ray absorption fine structure (EXAFS) spectroscopy.The geometric optimization and energy calculation of nickel sulfate hydrated clusters of the molecular formula [NiSO4(H2O)n ]^0 (n=1-12) were determined via DFT using the B3LYP method.Several possible initial structures were considered for clusters of each size to locate the equilibrium geometry.Based on the DFT calculation,the favorable structure of Ni^2+ includes the six-coordinated form of [NiSO4(H2O)n ]^0 clusters.The results of hydration energy calculation suggest that the six-coordinated contact ion pair (CIP) is the stable configuration for small hydration clusters (n≤5),while the solvent-shared ion pair (SSIP) represents the favorable structure for medium hydration clusters (6≤n≤10).The solvent is separated by x water molecules (xSIP,x≥2 is the number of water molecule between Ni^2+ and SO4^2-) in larger hydration clusters (n≥11).The EXAFS analysis of the NiSO 4 aqueous solutions and NiSO4 ·6H2O solid established that Ni^2+ was surrounded by six water molecules tightly forming an octahedral structure in the first hydration shell,and no CIP was found from 0.70 mol/L to 2.22 mol/L (near saturation).The Ni-O distance and coordinated number were 2.040±0.020 and 6.0±1.0,respectively.These results are consistent with the DFT calculations for [NiSO4(H2O)n ]^0 clusters.DFT and EXAFS are powerful techniques that can be used to enhance the resolution of NiSO 4 solution microstructure.

Three-body Faddeev calculations for _(ΛΛ)^(6)He and _(ΩΩ)^(6)He hypernuclei

We study the ground-state properties of the _(YY)^(6)He double hyperon for _(ΛΛ)^(6)He and _(ΩΩ)^(6)He nuclei in a threebody model(Y+Y+α).We solve two coupled Faddeev equations corresponding to the three-body configurations(αY,Y)and(YY,α)in configuration space with the hyperspherical harmonics expansion method by employing the most recent hyperon-hyperon interactions obtained from lattice QCD simulations.Our numerical analysis for _(ΛΛ)^(6)He,using threeΛΛlattice interaction models,leads to a ground state binding energy in the(-7.468,-7.804)MeV domain and the separations <r_(Λ-Λ)>and <r_(α-Λ)>in the domains of(3.555,3.629)fm and(2.867,2.902)fm,respectively.The binding energy of the double-Ω hypenucleus _(ΩΩ)^(6)He leads to -67.21 MeV and consequently to smaller separations <r_(Ω-Ω)>=1.521 fm and <r_(α-Ω)>=1.293 fm.In addition to geometrical properties,we study the structure of ground-state wave functions and show that the main contributions are from the s-wave channels.Our results are consistent with the existing theoretical and experimental data.