The coordination-dependent force field of Tersoff for covalently bonded Si has been used to calculate the cleavage force as a function of interplanar separation and hence to estimate surface energies. This force field is already fitted to density functional results. The relation to bond-breaking and electron correlation will be emphasized. Finnis-Sinclair-type many-body potentials have then been used to treat some d-electron metals. In particular, results for cleavage force in bcc Fe will be presented, and also some calculations as two perfectly planar Fe surfaces are `rubbed together' at different interplanar separations. Finally, lattice dynamical models for the steady-state propagation of a screw dislocation, and then of a crack, will be used, again within a bond-breaking type of force field. For the screw dislocation propagation, a solitary wave equation is shown to follow in the ‘almost continuum' limit. Energy radiated by phonons as the dislocation moves can thereby be calculated.

The electronic structures of strained Si1-x-yGexCy (y£0.09) alloys on Si(001) have been studied by the ab initio pseudopotential method within the local density functional theory. The variations of the minimum band gap, the valence-band offset and the strain properties in the heterojunction interface are calculated together with the average bond energy theory. It is found that the dependences of the minimum band gap and the valence-band offset on the alloy composition change around the point of zero lattice mismatch. A comparison between our theoretical results and the available experimental data indicates that some of the contradictions from different research groups can be reasonably explained.

Ab initio total energy calculations are used to simulate the building of equiatomic solid Apb alloys (A=Li, Na, K) with A4Pb4 clusters which are particularly stable in the gas phase. The eight clusters per unit cell were drawn together by shrinking the cell in stages, and allowing full atomic relaxation at each stage. Charged Pb4 tetrahedral units dominate the structural and electronic properties, and these units are remarkably robust and insensitive to their alkali environment. The stability of the Pb4 units diminishes as we progress from K to Li and lead to their absence in the LiPb alloy in accordance with experiment. The distance between Pb4 units seems to be the critical factor responsible for the structural trends, which is determined by the atomic size of the alkali.

Progress in the development of phenomenological models for the microscopic interactions in the halides of polyvalent metals is reviewed, with main attention to neutral and ionized molecular states and to the melts of these materials. The following physical problems are discussed: (1) bond bending in the molecules of the alkaline-earth halides; (2) binding of molecular dimers and halogen transfer reactions relevant to the melts of trivalent metal halides; (3) stability of molecular ions in liquid mixtures of polyvalent metal halides and alkali halides; and (4) stability of molecular ions and reduced-valence states in molten cryolite under addition of sodium metal.

Experimental results of the temperature dependence of critical resolved shear stresses (CRSS) of Mo, Fe, Al and Mg single crystals are shown. Associating reports in recent years, we point out that the approximate exponential relationship between CRSS and the absolute temperature at least in the region of the steep temperature dependence range of many materials is more common, even for bcc, fcc, and hcp single crystals, polycrystals and other covalent crystals, provided that the slip plane and slip direction are kept the same. Successful explanation with atomic force law shows that the interatomic forces (electronic structure) play a decisive role in determining the temperature dependence of yield stresses for a large number of materials.

By using Morse potential model, we calculate the temperature dependence of critical resolved shear stress (CRSS) of some single crystals. Dislocation-phonon interaction is considered in this paper. Theoretical calculations fit experimental law well. Investigations show: interatomic force is the physical intrinsic that controls the plastic deformation processing of materials, and the temperature dependence of CRSS mainly comes from the temperature dependence of dislocation vibration.

In this paper, we deduce the analytical form of many-body interatomic potentials based on the Green’s function in tight-binding representation. The many-body potentials are expressed as the functions of the hopping integrals, which are the physical origin of cohesion of atoms. For the simple case of s-valent system, the inversion of the many-body potentials is discussed in detail by using the lattice inversion method.

A transferable tight-binding potential for Ni has been developed. Molecular dynamics methods and simulated annealing techniques have been used to study the structural properties of Ni clusters with this potential. We have obtained the structures of some Ni clusters. The average coordination number, ionization potentials and the stability of clusters have also been calculated.

The role of grain-boundary (GB) in the melting for å=5 bicrystals of B2 NiAl is investigated by molecular-dynamics simulation. The thermodynamic properties of the boundary are monitored over a wide temperature range including the thermodynamic melting point Tm, which is determined by using a many-body potential fitted to NiAl. A thermal disorder transition in the GB region occurs well below the melting point. Our results indicate that such a transition is a continuous process and there is no evidence of premelting, which is entirely in accord with experimental results and theoretical prediction. Moreover, we also find that the superheated temperature range of this intermetallic alloy is much wider than that of some elemental metals.

A computer program has been developed for the molecular dynamics calculation of ionic or strong-ionic covalent systems. Ewald summation algorithm and Keating potential model are adopted to calculate the long-range Coulomb interaction and the short-range bonding forces, respectively. A theoretical study on the domain boundary structures in epitaxial wurtzite GaN film is accomplished with the program. The calculation result is used in the structure formation explanation of an interesting defect observed by HREM experiment.

A simple analytic modified embedded atom method (MEAM) including a modified term for hcp metals has been developed from the MEAM applied to the fcc and bcc metals. The enthalpies of formation of all binary alloy systems for eight transition hcp metals are calculated with the MEAM. The calculations are in agreement with the experimental data available and results calculated from the Miedema theory. One can conclude that our MEAM is also effective to apply to the hcp metals and their alloys.

A simple analytic embedded atom method for bcc Fe and fcc Al metals is used to calculate the thermodynamic properties of the disordered solid solution and ordered intermetallic alloys of Fe aluminides. The thermodynamic properties, such as the dilute-limit heats of solution, formation enthalpies of disordered solid solutions and intermetallic compounds (Fe3Al in the D03 structure type, FeAl in the B2 structure type, and Fe13Al3) are in good agreement with the experimental data, and with the results calculated using the first principles and Miedema theory.

The effects of ternary solutes Ti, Co, V, Cr, Ta, W and Mo on the D03 phase stability of Fe3Al intermetallics are investigated by tight-binding linear Muffin-tin orbital method. The predicted site preferences of these elements in Fe3Al are in agreement with the experimental observations. The calculated local magnetic moment of Fe3Al is identical to the experimental. In addition, it is found that the D03 phase stability of Fe3Al doped with Ti, V, Co and Cr depends on ‘energy gap’ of energy band near Fermi level, while the D03 phase stability of Fe3Al doped with Ta, W and Mo may be affected by Madelung energy.

In this paper the persistent currents of ideal toroidal single-wall carbon nanotubes (TSWNTs) are calculated from the tight-binding model and the periodic boundary conditions. The electronic structure and persistent current of a TSWNT strongly depend on its helicity and longitudinalcircumference, making the TSWNTs a geometry-sensitive kind of materials. The interatomic carbonic interactions other than ppp-type are also studied and are found to introduce more steps to the persistent current. The diamagnetic-paramagnetic transitions occur more frequently, and the persistent current depends on the interaction energy values, while the periodicity of magnetic flux preserves.

The moving nonlinear excitations (intrinsic localized vibrational modes) for one-dimensional homogeneous monoatomic lattice with quartic anharmonicity are obtained analytically by means of the semidiscrete approximation, with which the carrier wave is treated explicitly while the envelope function is described in the continuum approximation. Besides the moving pulse-like type of excitations, which was found previously in both analytical and numerical works, we find that the moving kink-like type of excitations can also exist. And the kink-like excitations appeared previously only in the stationary form for such a lattice system.

We present a new series of two-dimensional decagonal tilings which are connected with each in five transformation rules. In this case, a real-space renormalization group scheme is developed to study physical properties of the decagonal systems in terms of Green's function theory.

Quantum dynamics in a family of generalized Fibonacci lattices have been studied. The autocorrelation function C(t) and the mean square displacement d(t) are investigated in the framework of a tight-binding Hamiltonian model. Numerical results show that C(t)- t-d and d(t)- tb. With the increase of modulation strength, d(t) exhibits a transition from ballistic (β=1) to non-ballistic behavior (0<β<1). However, we have 0<δ<1 in any case, and d decreases upon increasing the modulation strength. Moreover, approximately self-similar oscillations for both C(t) and d(t) are observed in the strong modulation cases.

The effects of the electric field on the electronic structures in electroluminescent polymers were studied with the tight-binding model including electron-phonon interactions plus an applied electric field. It is found that the applied electric field changes both the energy levels and the electronic wavefunctions in electroluminescent polymers: applied field induces two localized electronic states near the midgap, and also polarizes these localized electronic states, so the polarization occurs at weak or moderate fields. In addition, the strong field will dissociate a bipolaron exciton and lead to photoluminescence quenching.

Er was doped into porous Si by immersing the porous Si sample in a saturated ErCl3:ethanol solution. Sharp and intense 1.54 mm photoluminescence caused by intra-4f-shell transitions in Er3+ ions was observed up to room temperature. It is shown that the immersing process is valid to dope Er in high concentration in porous Si. Time resolved study of the Er-doped porous Si revealed that the doped Er3+ ions are excited by energy transfer from photo-generated electron-hole pairs in the host. The energy back transfer process from the excited 4f-electrons in the Er3+ ion to the host is not a dominant factor to quench the Er-related emission in porous Si. Our results are well explained by a proposed model in which an intermediate state was introduced.

We study the effect of dissipative transport of two-band systems in a static electric field. With the help of numerical solutions of a stochastic Liouville equation for the density matrix, we find that the Markoffian dephasing will take electrons, which are initially located in one band to equal population of the two bands, instead of undergoing Zener resonance, as they do in the absence of scattering.

The substitution behavior of some alloying elements in CoZr is investigated using the discrete variational Xa cluster method. The method proposed by the author to predict the substitution behavior is amended to consider the local lattice relaxation. A diagram is drawn based on the binding energies of clusters with alloying elements taking either Co or Zr site. Two straight lines on the diagram separate the alloying elements into three groups with different substitution behavior. The elements above the upper line will take Zr sites and those below the lower line will take Co sites regardless of the composition. The substitution behavior of elements in between the two lines will be affected by the alloy composition. The concept of site competition and step ordering is proposed.

The correlation effects among the polaronic and one-phonon coherent and two-phonon squeezed states induced by the motion and density fluctuation of the electrons change the state and properties of the strongly coupled electron-phonon systems and make the ground state energy decrease, the binding energy of the polarons increase, the CDW ordering enhance and the quantum fluctuation effect of the lattice phonons weaken.

The spin-dependent interfacial tunneling and the corresponding tunnel-type magnetoresistance (TMR) have been observed in granular perovskite La1-xSrxMnO3 with x from 0.05 to 0.45. Study shows that the interfacial tunneling originates from the magnetic difference between the grain core and the surface, and the TMR stems from the field-induced change of magnetic order in the interface.

The occurrence of both band-like and atom-like Auger spectra involving valence band electron of d-transition metals is discussed based on the two-step model of the Auger electron emission, i.e. an initial core-hole is first generated and the Auger transition occurs between the core-hole and the valence states. The occupied valence states relax to screen the core-hole which results in a redistribution of the valence electrons. The electronic states concerned by the Auger transition are calculated by the FLAPW method. There is a clear relation between band-like and atom-like features of the spectra and the different responses of these metals to the existence of a core-hole.

The elastic pair potential model of liquid crystal molecules was described. On the basis of Poniewiersky-Stecki statistical theory of the elastic constants of nematic liquid crystals, the effects of non-ideal rigid repulsion between molecules on the elastic constants of nematics were studied.

The fractal growth and form is considered by molecular dynamics and simulated using computer.

The electronic features in a proposed organic ferromagnet is presented by the first-principle scheme. A specific p band is dominant in this organic ferromagnet.

The ESR characteristics of boron-doped fullerene prepared by arc vaporization of B2O3 powder and graphite in a helium ambient are investigated for the first time. It is found that the obtained ESR spectrum of boron-doped fullerene is attributed to two components with the same g value of around 2.0025.

The phonon density of states of YBa2Cu3O6.92 is obtained with the method of Fourier deconvolution and Tikhonov’s regularization technique from the experimental specific heat data. The result is compared with that of neutron inelastic scattering.

Ballistic transport of Q1D electrons through multiple magnetic barriers is investigated. It is shown that ballistic conductance peaks disappear progressively with the increase of the oscillation frequency of the confining parabolic potential.

There are some new results about photovoltaic transient response in the new effect. We suggest a theoretical model to explain the effect reasonably. The theoretical calculation results agree with that in experiments.

Uncovered parts on substrate are the source of nucleation of thin films. A series of new correction formulas are given for the well-known theory of thin films.

a-Si:C:N:H thin films have been deposited at room temperature by r.f. reactive-sputtering of a Si target in an Ar+H2+N2+CH4 gas mixture. Fourier transform infrared-absorption spectroscopy and optical absorption spectra have been investigated for the films. The study shows that the film structure and optical, electrical properties are obviously modified readily by controlling the process parameters of deposition. The nitrogen-rich a-Si:C:N:H films are thermally stable within the temperature ranging from 200 to 800°C. They are of interest for the potential applications in electronic devices.

The conductivity of phosphorus-doped hydrogenated nanocrystalline Si (nc-Si:P:H) films is 10-1-101 W-1˙cm-1, two order of magnitude higher than that of undoped hydrogenated nanocrystalline Si (nc-Si:H) film. A series of conductivity temperature dependence curves show that the kink point temperature almost existing in hydrogenated amorphous Si (a-Si:H) film disappears.

A new type free-standing long-chain stable polyacetylene film was polymerized by modifying Narrmann’s method. The conductivity of this film was over 104 s/cm after doping with iodine. The most interesting point is that the conductivity increased stepwisely upon iodine doping concentration.

The study of nanocrystalline SnO2 (n-SnO2) and SiO2-doped SnO2 (n-Si-SnO2) samples prepared by the sol-gel process showed that SiO2 doping can effectively restrained the growth of nanocrystalline SnO2 grains, thus improving thermal stability of the materials.

(Fe7Co3)0.15(SiO2)0.85 granular alloy solid was prepared successfully using sol-gel method. The samples with different reducing temperatures were investigated by X-ray diffractometer(XRD), transmission electron micrography(TEM) and vibrating sample magnetometer(VSM). The average particle sizes of the samples were also calculated from Scherrer formula. The magnetic properties of (Fe7Co3)0.15(SiO2)0.85 were studied in detail.

The Co content dependence of crystal structure and specific magnetization of Fe1-xCox-SiO2 granular solid prepared by the sol-gel method have been studied. It is found that the crystal structure, lattice parameter and specific magnetization of the FeCo alloy particles depend on the Co content.

To make a kind of magnetic field caused by the strip-wound cut cores made from amorphous alloy, it can be used for the maker of magnetic distilled water with the function of magnetic cure and health protection.

This paper analyses the peculiar acting mechanism of artificial neural network (ANN) tech, and explores the great immediate significence for the intelligent sci-tech (IST) to research and develop the nano-tech.