Calculation of scattering parameters for ultracold 6Li-TLi elastic collisions＊

This paper theoretically studies the elastic scattering properties in a mixture of 6Li and 7Li atoms at cold and ultracold temperatures. Based on the constructed accurate interatomic potential of the triplet state for 6Li7Li mixture by the mass scaling method, it calculates the interspecies s-wave scattering lengths and the p-wave scattering lengths by the variable phase method and the semiclassical method, respectively. The scattering length is in good agreement with the experiment. The partial-wave and total cross sections are also calculated and a rich resonance structure is found.     

Calculation of scattering parameters for ultracold ~6 Li-~7 Li elastic collisions

This paper theoretically studies the elastic scattering properties in a mixture of 6 Li and 7 Li atoms at cold and ultracold temperatures.Based on the constructed accurate interatomic potential of the triplet state for 6 Li 7 Li mixture by the mass scaling method,it calculates the interspecies s-wave scattering lengths and the p-wave scattering lengths by the variable phase method and the semiclassical method,respectively.The scattering length is in good agreement with the experiment.The partial-wave and total cross sections are also calculated and a rich resonance structure is found.     

Chemisorption of Au on Si（001） surface

The chemisorption of one monolayer of Au atoms on an ideal Si(001) surface is studied by using the self-consistent tight binding linear muffin-tin orbital method. Energies of the adsorption system of a Au atom on different sites are calculated. It is found that the most stable position is A site (top site) for the adsorbed Au atoms above the Si(001) surface. It is possible for the adsorbed Au atoms to sit below the Si(001) surface at the B_1 site(bridge site), resulting in a Au－Si mixed layer. This is in agreement with the experiment results. The layer projected density of states is calculated and compared with that of the clean surface. The charge transfer is also investigated.     

Elastic Scattering of Ultracold ^133Cs and SSRb Atoms in Triplet State

Elastic scattering properties of the ultracold interaction for the triplet state of ^133Cs and ^85Rb atoms are studied using two kinds of potentials by the same phase Ф. One is the interpolation potential, and another is Lennard-Jones potential （LJl2,6 ）. The radial Schrodtinger equation is also solved using two computational methods, the semiclassical method （WKB）, and the Numerov method. Our results are found to be in an excellent agreement with the more recent theoretical values. It shows that the two potentials and methods are applicable for studying ultracold collisions between the mixing alkali atoms.     

Chemisorption of Fe on Au-passivated Si（001） surface

The chemisorption of one monolayer of Fe atoms on a Au-passivated Si(001) surface is studied by using the self-consistent tight-binding linear muffin-tin orbital method. The Fe adatom chemisorption on an ideal Si(001) surface is also considered for comparison. The chemisorption energy and layer projected density of states for a monolayer of Fe atoms on Au-passivated Si(001) surface are calculated and compared with that of the Fe atoms on an ideal Si(001) surface. The charge transfer is investigated. It is found that the most stable position is at the fourfold hollow site for the adsorbed Fe atoms, which might sit below the Au surface. Therefore there will be a Au－Fe mixed layer at the Fe/Au－Si(100) interface. It is found that the adsorbed Fe atoms cannot sit below the Si surface, indicating that a buffer layer of Au atoms may hinder the intermixing of Fe atoms and Si atoms at the Fe/Au－Si(001) interface effectively, which is in agreement with the experimental results.     

Interesting Features of Ionization Potentials for Elements(Z≤119)along the Periodic Table

The ionization potential(IP) is a basic property of an atom,which has many applications such as in element analysis.With the Dirac-Slater methods(i.e.,mean field theory),IPs of all occupied orbitals for elements with atomic number(Z ≤119) are calculated conveniently and systematically.Compared with available experimental measurements,the theoretical accuracies of IPs for various occupied orbitals are ascertained.The map of the inner orbital IPs with good accuracies should be useful to select x-ray energies for element analysis.Based on systematic variations of the first IPs for the outermost orbitals in good agreement with experimental values as well as other IPs,mechanisms of electronic configurations of all atomic elements(Z ≤ 119) along the periodic table are elucidated.It is interesting to note that there exist some deficiencies of the intermediate orbital IPs,which are due to electron correlations and should be treated beyond the mean Geld theory.     

Exchange Coupling and Stability of SmCo7-xHfx

Electronic structure of SmCo7-xHfx compound is calculated by using the multi-scattering Xα method. It is shown that a few of electrons can transfer to the Sm 5d orbital due to orbital hybridization between Sm and Co atoms. The 3d-5d coupling is stronger, which is the main reason to result in the long-range ferromagnetic order between Sm and Co atoms in SmCo7-xHfx. According to the Stoner criterion, the result of spin-unpolarized calculation for the Sm5Co32Hf2 duster could lead to a better understanding of why the ferromagnetic SmCo7-xHfx is a stable phase. For the Sm5Co32Hf2 duster the Fermi level is situated at the overall maximum of the density of states. Moreover the duster wavefunctions at EF are antibonding and hence highly localized in real space, which would lead to a large value for the duster Stoner integral. Thus a rationalization for the magnetic stability of SmCo7-xHfx has been obtained.     

Molecular Dynamics Simulations of Helium Behaviour in Titanium Crystals

Molecular dynamics simulations are performed to investigate the behaviour of helium atoms in titanium at a temperature of 30OK. The nucleation and growth of helium bubble has been simulated up to 50 helium atoms. The approach to simulate the bubble growth is to add helium atoms one by one to the bubble and let the system evolve. The titanium cohesion is based on the tight binding scheme derived from the embedded atom method, and the helium-titanium interaction is characterized by fitted potential in the form of a Lennard-Jones function. The pressure in small helium bubbles is approximately calculated. The simulation results show that the pressure will decrease with the increasing bubble size, while increase with the increasing helium atoms. An analytic function about the quantitative relationship of the pressure with the bubble size and number of helium atoms is also fitted.     

Investigations on molecular constants of the CD（X^2∏） radical and elastic collisions between ground-state C and D atoms at low temperatures

The potential energy curve of the CD(X~2Π) radical is obtained using the coupled-cluster singles-doublesapproximate-triples [CCSD(T)] theory in combination with the correlation-consistent quintuple basis set augmented with diffuse functions,aug-cc-pV5Z.The potential energy curve is fitted to the Murrell-Sorbie function,which is used to determine the spectroscopic parameters.The obtained D0,De,Re,ωe,ωeχe,αe and Be values are 3.4971 eV,3.6261 eV,0.11197 nm,2097.661 cm 1,34.6963 cm 1,0.2083 cm 1 and 7.7962 cm 1,respectively,which conform almost perfectly to the available measurements.With the potential obtained at the UCCSD(T)/aug-cc-pV5Z level of theory,a total of 24 vibrational states have been predicted for the first time when J = 0 by solving the radial Schr¨odinger equation of nuclear motion.The complete vibrational levels,the classical turning points,the inertial rotation constants and centrifugal distortion constants are reproduced from the CD(X~2Π) potential when J = 0,and are in excellent agreement with the available measurements.The total and the various partial-wave cross sections are calculated for the elastic collisions between the ground-state C and D atoms at energies from 1.0×10 11 to 1.0×10 4 a.u.when the two atoms approach each other along the CD(X~2Π) potential energy curve.Only one shape resonance is found in the total elastic cross sections,and the resonant energy is 8.36×10 6 a.u.The results show that the shape of the total elastic cross section is mainly dominated by the s partial wave at very low temperatures.Because of the weak shape resonances coming from higher partial waves,most of them are passed into oblivion by the strong total elastic cross sections.     

First-Principle-Based Calculations of the Hugoniot of Cu

The equation of state of face-centred-cubic (fcc) copper crystals at pressures up to 500 GPa and relative volume to 0.55 have been evaluated by using the full-potential linear muffin-tin orbital (FPLMTO) total-energy method combining with a mean-field model of the vibrational partition function. The mean-field is constructed from the sum of all the pair potentials between the reference atom and the others of the system. The calculated properties are in good agreement with the available shock-wave experimental measurements.     

Initial Processes of Sulfur Adsorption on Si（100） Surface

The adsorption of one monolayer S atoms on ideal Si（100） surface is studied by using the self-consistent tight binding linear muffon-tin orbital method. Energies of adsorption systems ors atoms on different sites are calculated. It is found that the adsorbed S atoms are more favorable on B1 site （bridge site） with a distance 0.131 nm above the Si surface. The .S, Si mixed layer might exist at S/Si（100） interface. The layer projected density of states are calculated and compared with that of the clean surface. The charge transfers are also investigated.     

Initial Processes of Hydrogen Adsorption on Si（100） Surface

The adsorption of one monolayer H atoms on an ideal Si(100) surface is studied by using the self-consistent tight binding linear muffin-tin orbital method. Energies of adsorption systems of H atoms on different sites are calculated.It is found that the adsorbed H atoms are more favorable on B1 site (bridge site) with a distance 0.056 nm above the Si surface. There does not exist reaction barrier at the Si surface. The layer projected density states are calculated and compared with those of the clean surface. The charge transfers are also investigated.     

The effective ionization coefficients and electron drift velocities in gas mixtures of CF3I with N2 and CO2 obtained from Boltzmann equation analysis

The electron swarm parameters including the density-normalized effective ionization coefficients(α-η)/N and the electron drift velocities V e are calculated for a gas mixture of CF3I with N2 and CO2 by solving the Boltzmann equation in the condition of a steady-state Townsend(SST) experiment.The overall density-reduced electric field strength is from 100 Td to 1000 Td(1 Td = 10-17V·cm2),while the CF3I content k in the gas mixture can be varied over the range from 0% to 100%.From the variation of(αη)/N with the CF3I mixture ratio k,the limiting field strength(E/N) lim for each CF3I concentration is derived.It is found that for the mixtures with 70% CF3I,the values of(E/N) lim are essentially the same as that for pure SF 6.Additionally,the global warming potential(GWP) and the liquefaction temperature of the gas mixtures are also taken into account to evaluate the possibility of application in the gas insulation of power equipment.     

Chemical modification of silicene

Silicene is a two-dimensional(2D) material, which is composed of a single layer of silicon atoms with sp2–sp3mixed hybridization. The sp2–sp3mixed hybridization renders silicene excellent reactive ability, facilitating the chemical modification of silicene. It has been demonstrated that chemical modification effectively enables the tuning of the properties of silicene. We now review all kinds of chemical modification methods for silicene, including hydrogenation, halogenation,organic surface modification, oxidation, doping and formation of 2D hybrids. The effects of these chemical modification methods on the geometrical, electronic, optical, and magnetic properties of silicene are discussed. The potential applications of chemically modified silicene in a variety of fields such as electronics, optoelectronics, and magnetoelectronics are introduced. We finally envision future work on the chemical modification of silicene for further advancing the development of silicene.     

Intermolecular Interaction Potentials of CH4-Ne Complex Calculated with Local Density Approximation Methods

The intermolecular interactions potentials for two configurations of CH4-Ne complex are calculated with localdensity approximation methods in the frame of density functional theory. It is found that the calculated potentialshave two minima when the distance between the carbon atom of CH4 and the Ne atom takes R = 5.80a.u.and 6.20a.u. for both the two configurations. For the edge configuration, the corresponding depth of thepotential is 0.0669536eV and 0.0671416eV. For the face configuration, the corresponding depth of the potentialis 0,0737956 eV and 0.0645506 eV. The global minimum occurs at R = 5.80 a.u. for the face configuration with adepth of the potential 0.0737956eV. The depths of our calculation are in better agreement with the experimentaldata than the quantum chemical calculation approach~ while the position of minimum potential for our calculationis underestimated.     

Computational Prediction to Two-Dimensional SnAs

By means of the particle-swarm optimization method and density functional theory calculations, the lowestenergy structure of SnAs is determined to be a bilayer stacking system and the atoms on top of each other are of the same types. Using the hybrid functional of Heyd–Scuseria–Ernzerhof, SnAs is calculated to be a semiconductor with an indirect band gap of 1.71 eV, which decreases to 1.42 eV with the increase of the bi-axial tensile stress up to 2%, corresponding to the ideal value of 1.40 eV for potential photovoltaic applications. Based on the deformation potential theory, the two-dimensional(2 D) SnAs has high electron motilities along x and y directions(1.63 × 10~3 cm~2 V~(-1)s~(-1)). Our calculated results suggest that SnAs can be viewed as a new type of 2 D materials for applications in optoelectronics and nanoelectronic devices.     

A Calculation Approach to Elastic Constants of Crystallines at High Pressure and Finite Temperature

Elastic constants of Na and Li metals are calculated successfully for temperatures up to 350K and pressures up to 30GPa using a scheme without involving any adjustable parameter.Elastic constants are assumed to depend only on an effective pair potential that is only determined by the average interatomic distance.Temperature has an effect on elastic constants by way of charging the equilibrium.The elastic constants can be obtained by fitting the relationship between total energy and strain tensor using the new set of lattice parameters obtained by calculating displacement of atoms at the finite temperature and at a fixed pressure.The relationship between the effective pair potential and the interatiomic distance is fitted by using a series of data of cohesive energy corresponding to lattice parameters.     

Calculation of Partition Function of QCD at Finite Chemical Potential

In equilibrium statistical field theory, the partition function has fundamental importance. In this paper we propose a direct and general method for calculating the partition function and equation of state of QCD at finite chemical potential. It is found that the partition function is totally determined by the dressed quark propagator at finite chemical potential up to a multiplicative constant. From this a criterion for the phase transition between the Nambu and the Wigner phases is obtained. This general method is applied to two specific cases： the free quark theory and QCD with a model dressed quark propagator having confinement features. In the first case, the standard Fermi distribution at T = 0 is reproduced. In the second case, we apply the conclusion in previous works to obtain the dressed quark propagator at finite chemical potential and find the unphysical result that the baryon number density vanishes for all values of chemical potential. The reason for this result is discussed.     

Modified Eyring viscosity equation and calculation of activation energy based on the liquid quasi-lattice model

Viscosity is an important physical parameter of fluid,and the Eyring viscosity equation is a popular viscosity theory.Based on the Eyring reaction rate equation and Boltzmann statistical theory,and including the probabilities of creating a hole in liquid and the transition to the neighboring hole,a modified Eyring viscosity equation was proposed.According to the structural characteristics of short-range order,liquid is treated as a quasi-lattice structure in a small region.The activation energy,which is the minimum energy needed for the molecule to jump to its neighboring hole because of the restriction of other molecules around it,was analytically calculated from an intermolecular Lennard-Jones potential function and a Stockmayer potential function.The viscosity values of 37 kinds of typical liquids at 25°C and the dependence of viscosity of three kinds of liquids on temperatures were calculated with this modified viscosity equation,and the calculated results agree with the experimental values to some extent.This work not only enriches the understanding of the mechanism of liquid viscosity,but also could provide some theoretical guides for the relevant studies and applications.