Continuum Skyrme Hartree-Fock-Bogoliubov theory with Green’s function method for neutron-rich Ca,Ni,Zr,and Sn isotopes

The possible exotic nuclear properties in the neutron-rich Ca,Ni,Zr,and Sn isotopes are examined with the continuum Skyrme Hartree-Fock-Bogoliubov theory in the framework of the Green’s function method.The pairing correlation,the couplings with the continuum,and the blocking effects for the unpaired nucleon in odd-A nuclei are properly treated.The Skyrme interaction SLy4 is adopted for the ph channel and the density-dependentinteraction is adopted for the pp chan-nel,which well reproduce the experimental two-neutron separation energies S_(2n)and one-neutron separation energies Sn.It is found that the criterion S_(n)>0 predicts a neutron drip line with neutron numbers much smaller than those for S_(2n)>0.Owing to the unpaired odd neutron,the neutron pairing energies−E_(pair)in odd-A nuclei are much lower than those in the neighbor-ing even-even nuclei.By investigating the single-particle structures,the possible halo structures in the neutron-rich Ca,Ni,and Sn isotopes are predicted,where sharp increases in the root-mean-square(rms)radii with significant deviations from the traditional rA^(1∕3)rule and diffuse spatial density distributions are observed.Analyzing the contributions of various partial waves to the total neutron densityρlj(r)∕ρ(r)reveals that the orbitals located around the Fermi surface-particularly those with small angular momenta-significantly affect the extended nuclear density and large rms radii.The number of neutrons Nλ(N_(0))occupying above the Fermi surfacen(continuum threshold)is discussed,whose evolution as a function of the mass number A in each isotope is consistent with that of the pairing energy,supporting the key role of the pairing correlation in halo phenomena.

From the Green's Function in Tight-Binding Representation to Interatomic Many-body Potentials

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 thesimple case of s-valent system, the inversion of the many-body potentials are discussed in detail by using the lattice inversion method.

Spectral Theorem of Many-Body Green's Functions When Complex Eigenvalues Appear

In this paper, an extended spectral theorem is given, which enables one to calculate the correlation functions when complex eigenvalues appear. To do so, a Fourier transformation with a complex argument is utilized. We treat all the Matsbara frequencies, including Fermionic and Bosonic frequencies, on an equal footing. It is pointed out that when complex eigenvalues appear, the dissipation of a system cannot simply be ascribed to the pure imaginary part of the Green function. Therefore, the use of the name fluctuation-dissipation theorem should be careful.

The Green's function of the harmonic horizontal force applied at the interior of the saturated half-space soil

By using integral transform methods, the Green(s functions of horizontal harmonic force applied at the interior of the saturated half-space soil are obtained in the paper. The general solutions of the Biot dynamic equations in frequency domain are established through the use of Hankel integral transforms technique. Utilizing the above- mentioned general solutions, and the boundary conditions of the surface of the half-space and the continuous conditions at the plane of the horizontal force, the solutions of the boundary value problem can be determined. By the numerical inverse Hankel transforms method, the Green(s functions of the harmonic horizontal force are obtainable. The degenerate case of the results deduced from this paper agrees well with the known results. Two numerical examples are given in the paper.

Searching for single-particle resonances with the Green’s function method

Single-particle resonances in the continuum are crucial for studies of exotic nuclei.In this study,the Green’s function approach is employed to search for single-particle resonances based on the relativistic-mean-field model.Taking^(120)Sn as an example,we identify singleparticle resonances and determine the energies and widths directly by probing the extrema of the Green’s functions.In contrast to the results found by exploring for the extremum of the density of states proposed in our recent study[Chin.Phys.C,44:084105(2020)],which has proven to be very successful,the same resonances as well as very close energies and widths are obtained.By comparing the Green’s functions plotted in different coordinate space sizes,we also found that the results very slightly depend on the space size.These findings demonstrate that the approach by exploring for the extremum of the Green’s function is also very reliable and effective for identifying resonant states,regardless of whether they are wide or narrow.

Solution of pavement temperature field in“Environment-Surface”system through Green's function

In order to simplify the boundary conditions of pavement temperature field,the "Environment-Surface" system which considered the natural environment and pavement surface was established.Based on this system,the partial differential equations of the one-dimensional heat conduction in the pavement were established on the basis of the heat transfer theory.Furthermore,the function forms of the initial and boundary conditions of the equations were created through the field experiments.The general solution of the pavement one-dimensional heat conduction partial differential equations was acquired by using Green's function,and the explicit expression of pavement temperature field under specific constraint conditions was derived.For the purpose of analysis,the pavement temperatures in different seasons were calculated using the explicit expression of pavement temperature field,and the calculation accuracy was analyzed through the comparison between measured and calculated values.Then,the relationship between fitting accuracy and calculation accuracy of pavement temperatures was analyzed.The analysis results show that: the usage of "Environment-Surface" system simplifies the calculation of pavement temperature field; the relative error between calculated and measured values is generally less than 7% and is seldom influenced by seasons; there is a positive correlation between the calculation accuracy and the fitting accuracy of pavement surface temperature; high fitting accuracy would result in less error of pavement temperature prediction.

Electronic Transport Calculations Using Maximally-Localized Wannier Functions

I present a method to calculate the ballistic transport properties of atomic-scale structures under bias. The electronic structure of the system is calculated using the Kohn-Sham scheme of density functionai theory （DFT）. The DFT eigenvectors are then transformed into a set of maximaily localized Wannier functions （MLWFs） [N. Maxzari and D. Vanderbilt, Phys. Rev. B 56 （1997） 12847]. The MLWFs are used as a minimai basis set to obtain the Hamitonian matrices of the scattering region and the adjacent leads, which are needed for transport calculation using the nonequilibrium Green＇s function formalism. The coupling of the scattering region to the semi-infinite leads is described by the self-energies of the leads. Using the nonequilibrium Green＇s function method, one calculates self-consistently the charge distribution of the system under bias and evaluates the transmission and current through the system. To solve the Poisson equation within the scheme of MLWFs I introduce a computationally efficient method. The method is applied to a molecular hydrogen contact in two transition metal monatomic wires （Cu and Pt）. It is found that for Pt the I-V characteristics is approximately linear dependence, however, for Cu the I-V characteristics manifests a linear dependence at low bias voltages and exhibits apparent nonlinearity at higher bias voltages. I have also calculated the transmission in the zero bias voltage limit for a single CO molecule adsorbed on Cu and Pt monatomic wires. While a chemical scissor effect occurs for the Cu monatomic wire with an adsorbed CO molecule, it is absent for the Pt monatomie wire due to the contribution of d-orbitals at the Fermi energy,

预测规则波浪中船舶运动和载荷的频域三维计算机程序

The development of an in-house computer program for determining the motions and loads of advancing ships through sea waves in the frequency domain,is described in this paper.The code is based on the potential flow formulation and originates from a double-body code enhanced with the regular part of the velocity potential computed using the pulsing source Green function.The code is fully developed in C++language with extensive use of the object-oriented paradigm.The code is capable of estimating the excitation and inertial radiation loads or arbitrary incoming wave frequencies and incidence angles.The hydrodynamic responses such as hydrodynamic coefficients,ship motions,the vertical shear force and the vertical bending moment are estimated.A benchmark container ship and an LNG carrier are selected for testing and validating the computer code.The obtained results are compared with the available experimental data which demonstrate the acceptable compliance for the zero speed whereas there are some discrepancies over the range of frequencies for the advancing ship in different heading angles.

Thermal Expansion Coefficients of Thin Crystal Films

The formulas for atomic displacements and Hamiltonian of a thin crystal film in phonon occupation number representation are obtained with the aid of Green's function theory. On the basis of these results, the formulas for thermal expansion coefficients of the thin crystal film are derived with the perturbation theory, and the numerical calculations are carried out. The results show that the thinner films have larger thermal expansion coefficients.

Effects of Coverage,Water,and Defects on Catechol/TiO2 Interface

Catechol adsorbed on TiO_(2)is one of the simplest models to explore the relevant properties of dye-sensitized solar cells.However,the effects of water and defects on the electronic levels and the excitonic properties of the catechol/TiO_(2)interface have been rarely explored.Here,we investigate four catechol/TiO_(2)interfaces aiming to study the influence of coverage,water,and defects on the electronic levels and the excitonic properties of the catechol/TiO_(2)interface through the first-principles many-body Green’s function theory.We find that the adsorption of catechol on the rutile(110)surface increases the energies of both the TiO_(2)valence band maximum and conduction band minimum by approximately 0.7 eV.The increasing coverage and the presence of water can reduce the optical absorption of charge-transfer excitons with maximum oscillator strength.Regarding the reduced hydroxylated TiO_(2)substrate,the conduction band minimum decreases greatly,resulting in a sub-bandgap of 2.51 eV.The exciton distributions in the four investigated interfaces can spread across several unit cells,especially for the hydroxylated TiO2substrate.Although the hydroxylated TiO_(2)substrate leads to a lower open-circuit voltage,it may increase the separation between photogenerated electrons and holes and may therefore be beneficial for improving the photovoltaic efficiency by controlling its concentration.Our results may provide guidance for the design of highly efficient solar cells in future.

Statistical Average of Spin Operators for Calculation of Three-Component Magnetization （II）： Solution of Equation

In this paper, the solution of Chebyshev equation with its argument being greater than 1 is obtained. The initial value of the derivative of the solution is the expression of magnetization, which is valid for any spin quantum number S. The Chebyshev equation is transformed from an ordinary differential equation obtained when we dealt with Heisenberg model, in order to calculate all three components of magnetization, by many-body Green＇s function under random phase approximation. The Chebyshev functions with argument being greater than 1 are discussed. This paper shows that the Chebyshev polynomials with their argument being greater than 1 have their physical application.

Theoretical Investigation of Exchange Bias in Compensated Cases

The exchange bias （EB） of the ferromagnetic （FM）/antiferromagnetic （AFM） bilayers in a compensated case is studied by use of the many-body Green＇s function method of quantum statistical theory. The so-called compensated case is that there is no net magnetization on the AFM side of the interface. Our conclusion is that the EB in this case is primarily from the asymmetry of the interracial exchange coupling strengths between the FM and the two sublattices of the AFM. The effects of the layer thickness, temperature and the interracial coupling strength oi2 the exchange bias HE are investigated. The dependence of HE on the FM layer thickness and temperature is qualitatively in agreement with experimental results. HE is nearly inversely proportional to FM thickness. When temperature varies, both HE and He decrease with temperature increasing. The anisotropy of the FM layer only slightly influence He, but does not influence HE.

Ab initio investigations of the charge transport properties of endohedral M@C_(20)(M=Na and K)metallofullerenes

Using density functional theory and quantum transport calculations based on nonequilibum Green＇s function formalism, we investigate the charge transport properties of endohedral M@C20（M = Na and K） metallofullerenes. Our results show that the conductance of C20 fullerene can be obviously improved by insertion of alkali atom at its centre. Both linear and nonlinear sections are found on the Ⅰ-Ⅴ curves of the Au-M@C20-Au two-probe systems. The novel negative differential resistance behaviour is also observed in Na@C20 molecule but not in K@C20.

Direct and Indirect Excitons in Two-Dimensional Covalent Organic Frameworks

Highly luminescent bulk two-dimensional covalent organic frameworks(COFs)attract much attention recently.Origin of their luminescence and their large Stokes shift is an open question.After first-principles calculations on two kinds of COFs using the GW method and Bethe-Salpeter equation,we find that monolayer COF has a direct band gap,while bulk COF is an indirect band-gap material.The calculated optical gap and optical absorption spectrum for the direct excitons of bulk COF agree with the experiment.However,the calculated energy of the indirect exciton,in which the photoelectron and the hole locate at the conduction band minimum and the valence band maximum of bulk COF respectively,is too low compared to the fluorescence spectrum in experiment.This may exclude the possible assistance of phonons in the luminescence of bulk COF.Luminescence of bulk COF might result from exciton recombination at the defects sites.The indirect band-gap character of bulk COF originates from its AA-stacked conformation.If the conformation is changed to the AB-stacked one,the band gap of COF becomes direct which may enhance the luminescence.

Improvement of the thermoelectric efficiency of pyrene-based molecular junction with doping engineering

In this study, the thermoelectric properties of pyrene molecule doped with boron and nitrogen atom at different sites of molecule are investigated using density functional theory and none-equilibrium Greens function formalism in the linear response regime. Our calculations show that when the impurities are added to the edge of the molecule, the anti-resonant peaks will appear in the transmission diagram in the vicinity of the Fermi energy level. So it increases the thermoelectric figure of merit of the system in comparison with the one that the impurity is located in the center of molecule. Additionally, the seebeck coefficient signs are not the same among the B, N, and N ＆ B doped devices, indicating that the types of the carriers can be changed with different types of doping.

Stability of conductance oscillations in carbon atomic chains

The conductance stabilities of carbon atomic chains （CACs） with different lengths are investigated by performing the- oretical calculations using the nonequilibrium Green＇s function method combined with density functional theory. Regular even-odd conductance oscillation is observed as a function of the wire length. This oscillation is influenced delicately by changes in the end carbon or sulfur atoms as well as variations in coupling strength between the chain and leads. The lowest unoccupied molecular orbital in odd-numbered chains is the main transmission channel, whereas the conductance remains relatively small for even-numbered chains and a significant drift in the highest occupied molecular orbital resonance to- ward higher energies is observed as the number of carbon atoms increases. The amplitude of the conductance oscillation is predicted to be relatively stable based on a thiol joint between the chain and leads. Results show that the current-voltage evolution of CACs can be affected by the chain length. The differential and second derivatives of the conductance are also provided.

Different noncollinear magnetizations on two edges of zigzag graphene nanoribbons

Based on density functional theory and non-equilibrium Green’s function method,we studied noncollinear magnetism and spin transport in a 180°domain wall made of zigzag graphene nanoribbon(ZGNR)with different noncollinear magnetic profiles on the top and bottom edges.Our results show that a helical domain wall on the top(bottom)edge and an abrupt domain wall on the bottom(top)edge can survive in the ZGNR.This indicates that such characteristic magnetization distribution can be obtained by some means,e.g.,the introduction of impurity on one edge.Compared to a wide ZGNR,a narrow ZGNR presents obvious coupling between the two edges which changes the magnetization and transmission greatly.As for the above-mentioned distinct magnetic profile,the spin transport is blocked in the abrupt domain wall due to strong spin flip scattering while remains unaffected in the helical domain wall due to the spin mixing effect.We deduce a formula of the transmission for various magnetic profiles of the ZGNRs.A new result based on this formula is that the transmission at the Fermi level can be zero,one,and two by tuning the edge magnetization.Our results provide insights into the noncollinear spin transport of the ZGNR-based devices.

Low-Bias Conductance Mechanism of Diarylethene Isomers:a First-Principle Study

The structure-property relationship of diarylethene(DAE)-derivative molecular isomers,which involve ring-closed and ring-open forms,is investigated by employing the nonequilibrium Green’s function formalism combined with density functional theory.Molecular junctions are formed by the isomers connecting to Au(111)electrodes through flanked pyridine groups.The difference in electronic structures caused by different geometry structures for the two isomers,particularly the interatomic alternative single bond and double bond of the ring-closed molecule,contributes to the vastly different low-bias conductance values.The lowest unoccupied molecular orbital(LUMO)of the isomers is the main channel for electron transport.In addition,more electrons transferred to the ring-closed molecular junction in the equilibrium condition,thereby decreasing the LUMO energy to near the Fermi energy,which may contribute to a larger conductance value at the Fermi level.Our findings are helpful for understanding the mechanism of low-bias conductance and are conducive to the design of high-performance molecular switching based on diarylethene or diarylethene-derivative molecules.

Exploring how hydrogen at gold-sulfur interface affects spin transport in single-molecule junction

Very recently,experimental evidence showed that the hydrogen is retained in dithiol-terminated single-molecule junction under the widely adopted preparation conditions,which is in contrast to the accepted view[Nat.Chem.11351(2019)].However,the hydrogen is generally assumed to be lost in the previous physical models of single-molecule junctions.Whether the retention of the hydrogen at the gold-sulfur interface exerts a significant effect on the theoretical prediction of spin transport properties is an open question.Therefore,here in this paper we carry out a comparative study of spin transport in M-tetraphenylporphyrin-based(M=V,Cr,Mn,Fe,and Co;M-TPP)single-molecule junction through Au-SR and Au-S(H)R bondings.The results show that the hydrogen at the gold-sulfur interface may dramatically affect the spin-filtering efficiency of M-TPP-based single-molecule junction,depending on the type of transition metal ions embedded into porphyrin ring.Moreover,we find that for the Co-TPP-based molecular junction,the hydrogen at the gold-sulfur interface has no obvious effect on transmission at the Fermi level,but it has a significant effect on the spin-dependent transmission dip induced by the quantum interference on the occupied side.Thus the fate of hydrogen should be concerned in the physical model according to the actual preparation condition,which is important for our fundamental understanding of spin transport in the single-molecule junctions.Our work also provides guidance in how to experimentally identify the nature of gold-sulfur interface in the single-molecule junction with spin-polarized transport.

Ferrimagnetism induced by asymmetrical ferromagnetic next-nearest-neighbour exchange interactions in an antiferromagnetic spin-1/2 zigzag chain

The magnetic properties of an antiferromagnetic bond alternating spin-l/2 zigzag chain with asymmetrical ferro- magnetic next-nearest-neighbour exchange interactions at finite temperature are investigated by using the many-body Green＇s function theory. It is found that the ferrimagnetic ordering does not appear in the symmetrical next-nearest- neighbour coupling case, and takes place only for the asymmetrical next-nearest-neighbour case at finite temperature rather than the ground state. Furthermore, as the asymmetry degree of the next-nearest-neighbour exchange inter- actions increases, the ferrimagnetism becomes more and more dominant. It is shown that the elementary excitation spectra are responsible for the observed magnetic behaviour.