价电子均衡电负性及其应用

提出一种不同于传统方法的价电子均衡方法来计算均衡电负性,包括分子电负性、基团电负性和原子电荷. 用分子电负性对烷烃和单取代烷烃分子的第一电离能进行关联,用基团电负性对某些分子的¹H NMR谱化学位移进行关联,用原子电荷对脂肪族胺、醇和醚分子的气相碱性进行关联. 所得各回归方程均有良好的相关性. 同时还在价电子均衡方法的基础上对Sanderson方法和Bratsch方法进行了修正,用于关联上述各性能,结果表明比相应的原方法更为有效.     

Exotic electronic states in the world of flat bands:From theory to material

It has long been noticed that special lattices contain single-electron flat bands(FB) without any dispersion. Since the kinetic energy of electrons is quenched in the FB, this highly degenerate energy level becomes an ideal platform to achieve strongly correlated electronic states, such as magnetism, superconductivity, and Wigner crystal. Recently, the FB has attracted increasing interest because of the possibility to go beyond the conventional symmetry-breaking phases towards topologically ordered phases, such as lattice versions of fractional quantum Hall states. This article reviews different aspects of FBs in a nutshell. Starting from the standard band theory, we aim to bridge the frontier of FBs with the textbook solidstate physics. Then, based on concrete examples, we show the common origin of FBs in terms of destructive interference,and discuss various many-body phases associated with such a singular band structure. In the end, we demonstrate real FBs in quantum frustrated materials and organometallic frameworks.     

Evolution of lone pair of excess electrons inside molecular cages with the deformation of the cage in e2@C60F60 systems

For unusual e(2)@C(60)F(60)(I(h), D(6h), and D(5d)) cage structures with two excess electrons, it is reported that not only the lone pair in singlet state but also two single excess electrons in triplet state can be encapsulated inside the C(60)F(60) cages to form single molecular solvated dielectrons. The interesting relationship between the shape of the cage and the spin state of the system has revealed that ground states are singlet state for spherical shaped e(2)@C(60)F(60)(I(h)) and triplet states for short capsular shaped e(2)@C(60)F(60)(D(6h)) and long capsular shaped e(2)@C(60)F(60)(D(5d)), which shows a spin evolution from the singlet to triplet state with the deformation of the cage from spherical to capsular shape. For these excess electron systems, the three ground state structures have large vertical electron detachment energies (VDEs (I) of 1.720-2.283 eV and VDEs (II) of 3.959-5.288 eV), which shows their stabilities and suggests that the large C(60)F(60) cage is the efficient container of excess electrons.     

Double counting in LDA + DMFT—The example of NiO

An intrinsic issue of the LDA + DMFT approach is the so called double counting of interaction terms. How to choose the double-counting potential in a manner that is both physically sound and consistent is unknown. We have conducted an extensive study of the charge-transfer system NiO in the LDA + DMFT framework using quantum Monte Carlo and exact diagonalization as impurity solvers. By explicitly treating the double-counting correction as an adjustable parameter we systematically investigated the effects of different choices for the double counting on the spectral function. Different methods for fixing the double counting can drive the result from Mott insulating to almost metallic. We propose a reasonable scheme for the determination of double-counting corrections for insulating systems.     

Exact results relating spin–orbit interactions in two-dimensional strongly correlated systems

A 2D square, two-bands, strongly correlated and non-integrable system is analysed exactly in the presence of many-body spin–orbit interactions via the method of Positive Semidefinite Operators. The deduced exact ground states in the high concentration limit are strongly entangled, and given by the spin–orbit coupling are ferromagnetic and present an enhanced carrier mobility, which substantially differs for different spin projections. The described state emerges in a restricted parameter space region, which however is clearly accessible experimentally. The exact solutions are provided via the solution of a matching system of equations containing 74 coupled, non-linear and complex algebraic equations. In our knowledge, other exact results for 2D interacting systems with spin–orbit interactions are not present in the literature.     

锗烯在金属衬底上的结构及电子性质的第一性原理研究

基于密度泛函理论的第一性原理计算,我们系统的研究了锗烯在Pt(111)、Au(111)和Al(111)表面的几何和电子结构.在这三种金属衬底上寻找到了9种结构,其中Al(111)-a、Au(111)-b和Pt(111)-c结构就是目前实验上已经成功制备的结构.我们还发现了其余6种目前理论和实验均没有提出,此外,Al(111)-b、Au(111)-a和Pt(111)-b结构的Dirac态仍保留,这些结构的形成能均大于范德瓦尔斯作用,因此非常有希望在实验上制备出来,应用于量子自旋霍尔效应的研究.本文的研究为锗烯在半导体衬底上的制备及应用奠定了理论基础.     

Electrochemical energy storage application of CuO/CuO@Ni–CoMoO4·0.75H2O nanobelt arrays grown directly on Cu foam

Supercapacitors are attracting huge research interest because they are expected to achieve battery-level energy density, and they have a longer calendar life and shorter charging time. However, due to the out shell materials without contact extra freeway for charge transports, the out shell materials have still limited contribution to high capacitance for array structure at high rates. Here, CO/CO@Ni-CMO NBs were designed and synthesized on Cu foam substrates with CuO NBs as cores or extra freeway and Ni–CoMoO₄·0.75H₂O nanobelt as shell by an easily synthetic method. CuO NBs will provide electron “superhighways” and extra outside freeway for charge storage and delivery. Besides, the Ni doped CoMoO₄·0.75H₂O NBs are conducive to the electrical conductivity, and open space among these nanosheets can act as an “ion reservoir”, the increment of active sites and the contribution of capacitive effects. Finally, the CO@Ni-CMO NBs directly grown on Cu foam could avoid the “dead” volume caused by the tedious process of mixing active materials with polymer binders/conductive additives. As expected, the CO/CO@Ni-CMO NBs exhibited the high specific capacitance, the good rate performance and the excellent electrochemical stability.