Local structure distortion and spin Hamiltonian parameters for Cr^(3+)-V_(Zn) tetragonal defect centre in Cr^(3+) doped KZnF_3 crystal

The quantitative relationship between the spin Hamiltonian parameters （D, g｜｜ Ag） and the crystal structure parameters for the Cr3＋-Vzη tetragonal defect centre in a Cr3＋ ：KZnF3 crystal is established by using the superposition model. On the above basis, the local structure distortion and the spin Hamiltonian parameter for the Cr3＋-Vzn tetragonal defect centre in the KZnF3 crystal are systematically investigated using the complete diagonalization method. It is found that the Vzn vacancy and the differences in mass, radius and charge between the Cr3＋ and the Zn2＋ ions induce the local lattice distortion of the Cr3＋ centre ions in the KZnF3 crystal. The local lattice distortion is shown to give rise to the tetragonal crystal field, which in turn results in the tetragonal zero-field splitting parameter D and the anisotropic g factor Ag. We find that the ligand F- ion along I001] and the other five F- ions move towards the central Cr3＋ by distances of A1 = 0.0121 nm and A2 = 0.0026 nm, respectively. Our approach takes into account the spin-rbit interaction as well as the spin-spin, spin other-orbit, and orbit-rbit interactions omitted in the previous studies. It is found that for the Cr3＋ ions in the Cr3＋：KZnF3 crystal, although the spin-rbit mechanism is the most important one, the contribution to the spin Hamiltonian parameters from the other three mechanisms, including spin- spin, spin-other-orbit, and orbit-orbit magnetic interactions, is appreciable and should not be omitted, especially for the zero-field splitting （ZFS） parameter D.

Ordered Charge Distribution in Superconductor Tl-Ba-Ca-Cu-O

The layered charges were calculated by means of constructing the complete structure of Tl Ba Ca Cu O superconductor. The weak link between Cu O and Ba O, or between Cu O and Tl O or Ba O or Tl O layers is explained with the aid of the charge of limited layer unit calculated from the values of ions obtained, in addition to the possibility of forming charges fluctuation, which depends on the π coordination covalent bond on Cu O plane and O Tl O structure. The possible chemical tight bonding orbitals are in accordance with those of other superconductors obtained by quantum theoretical method, which occur at Cu 3d (x 2-y 2) and O 2p x,y . The valence band composed of Cu 3d and O 2p orbital energy levels is obviously an energy band of conduction. The ordered charge on layers is the main reason that raises T c of superconductors. The difference of electronic structure of ab plane and c axis leads to the anisotropy properties.

The Scope of the Structural Completeness in the Class of all Over-Systems of the Classical Functional Calculus with Identity

This paper is the continuation of the paper [13]. Namely, in [13], the scope of the structural completeness in the class of all over-systems of the classical predicate calculus, has been established. In this paper we establish the scope of the structural completeness in the class of all over-systems of the classical functional calculus with identity.

Arc-length technique for nonlinear finite element analysis

Nonlinear solution of reinforced concrete structures, particularly complete load-deflection response, requires tracing of the equilibrium path and proper treatment of the limit and bifurcation points. In this regard, ordinary solution techniques lead to instability near the limit points and also have problems in case of snap-through and snap-back. Thus they fail to predict the complete load-displacement response. The arc-length method serves the purpose well in principle, received wide acceptance in finite element analysis, and has been used extensively. However modifications to the basic idea are vital to meet the particular needs of the analysis. This paper reviews some of the recent developments of the method in the last two decades, with particular emphasis on nonlinear finite element analysis of reinforced concrete structures.

Design, synthesis and anti-proliferative effects in tumor cells of new combretastatin A-4 analogs

A total of 11 novel combretastatin A-4（CA-4） analogs were designed, synthesized, and evaluated for the anti-proliferative effects in tumor cells. The compounds represent four structural classes：（i）hydrogenated derivatives,（ii） ethoxyl derivatives,（iii） amino derivatives and（iv） pro-drugs. Biological evaluations demonstrate that multiple structural features control the biological potency. Three of the compounds, sit-1, sit-2 and sit-3, have potent anti-proliferative activity against multiple cancer cell lines. Their pro-drugs were synthesized to increase water solubility. Structure–activity relationship study and Surflex-Docking were studied in this paper. These results will be useful for the design of new CA-4 analogs that are structurally related to the SAR study.