Zhang Cai-Rong

Spiral Wave in Small-World Networks of Hodgkin-Huxley Neurons

The effect of small-world connection and noise on the formation and transition of spiral wave in the networks of Hodgkin–Huxley neurons are investigated in detail. Some interesting results are found in our numerical studies. i) The quiescent neurons are activated to propagate electric signal to others by generating and developing spiral wave from spiral seed in small area. ii) A statistical factor is defined to describe the collective properties and phase transition induced by the topology of networks and noise. iii) Stable rotating spiral wave can be generated and keeps robust when the rewiring probability is below certain threshold, otherwise, spiral wave can not be developed from the spiral seed and spiral wave breakup occurs for a stable rotating spiral wave. iv) Gaussian white noise is introduced on the membrane of neurons to study the noise-induced phase transition on spiral wave in small-world networks of neurons. It is confirmed that Gaussian white noise plays active role in supporting and developing spiral wave in the networks of neurons, and appearance of smaller factor of synchronization indicates high possibility to induce spiral wave.

First-Principle Study of H2 Adsorption on Mg3N2(110) Surface

The adsorption of H2 on two kinds of Mg3N2(110) crystal surface is studied by first principles. Adsorption sites, adsorption energy, and the electronic structure of the Mg3N2 (110)/H2 systems are calculated separately. It is found that H2 is mainly adsorbed as chemical adsorption, on these sites the H2 molecules are dissociated and the H atoms tend to the top of two N, respectively, forming two NH, or the H atoms tend to the same N forming one NH2. There are also some physical adsorption sites. One of the bridge sites of Mg3N2(110) surface is more favorable than the other sites. On this site, H atoms tend to the top of two N, forming two NH. This process belongs to strong chemical adsorption. The interaction between H2 molecule and Mg3N2(110) surface is mainly due to the overlap-hybridization among H 1s, N 2s, and N 2p states, covalent bonds are formed between the N and H atoms.

Structures and electronic properties of SimN8-m(0 < m < 8) clusters: a density functional theory study

The geometries, electronic structures and related properties of SimN8-m(0 < m < 8) clusters are studied using density functional theory (DFT) with hybrid functional B3LYP. The calculated results reveal several trends. For any stoichiometric clusters, the lowest energy isomers with an alteration of N and Si atoms are favourable in energy if the numbers of Si and N atoms are large enough to form ... Si–N–Si–N... alternative chains. The bond lengths of single Si–N bonds are very close to the corresponding values of the bulk and other Si–N clusters. The geometries for N-rich and Si4N4 clusters are planar structures, but three-dimensional structures are favourable in energy for Si-rich clusters. With the increase of m, the isotropic polarizability and average polarizability increase, the total binding energies generally decrease, the HOMO-LUMO gap and vertical ionization potential oscillate with increasing number of valence electrons, and their values with even valence electrons are larger than those with odd valence electrons. The atomic charges, IR and Raman properties are also reported.

Effect of a magnetic field on the energy levels of donor impurities in the ZnO parabolic quantum well

Energy levels of a donor impurity in the ZnO parabolic quantum well under the magnetic field are investigated using the variational method. The binding energy of the ground state, the energies of 2p± state and 1s ! 2p transition energies of a hydrogenic donor in the ZnO parabolic quantum well are numerically calculated as a function of the strength of magnetic field for different parabolic potential fields. The results show that the external magnetic field has an obvious influence on the binding energies and the 1s ! 2p transition energies of a hydrogenic donor. The 1s to 2p transition energy increases linearly with the strength of magnetic field, but the 1s to 2p transition energy decreases when the strength of magnetic field increases for the small field strength. Compared to the GaAs parabolic well, the donors are more tightly bound to the ZnO parabolic well and the influence of external magnetic field on the binding energy of a donor is much stronger in the ZnO parabolic well.

DFT study on the structure and spectra of Ga5P5 cluster

In this paper, possible structures of Ga5P5 cluster were optimized by using density functional method with generalized gradient correction (B3LYP). The electronic structure of the isomers with lower energy was studied. The most stable structure obtained for Ga5P5 is a distorted pentaprism. The Ga-P bond formed in the cluster is strongly ionic. Based on NBO analysis, an average value of 0.59 electron transfers from Gallium to Phosphorus. The bond length 2.33–2.43 A is around the value in bulk GaP. The HOMO-LUMO gap is about 2.2 eV. The dipole moment and polarizability are calculated, and the IR and Raman spectra are also presented.