Equilibrium molecular dynamics calculation of the bulk viscosity of liquid water

Twenty independent equilibrium molecular dynamics simulations were performed in NVE ensemble to calculate the bulk viscosity of water at a temperature of 303 K and a density of 0.999 gcm^?3. The energy of each simulation with a production time of 200ps was conserved within 1 part in 10⁴. By stopping the velocity-scaling procedure at a proper step, the energies of independent simulations were specified precisely. This caused the simulations of different start configurations to sample the same NVE ensemble. The shear viscosity of SPC/E water obtained in the present study was 6.5±0.4 × 10^?4 Pas, which is in close agreement with a previous calculation in the NVT ensemble (Balasubramanian, S., Mundy, C. J., and Klein, M. L., 1996, J. clzern. Phys., 105, 11 190). The bulk viscosity was 15.5 ± 1.6 × 10^?4 Pas, which is 27% smaller than the experimental value. Thus, like its behaviour in predicting the shear viscosity, the SPC/E model also underestimates the bulk viscosity of real water.     

High-frequency dynamics in metallic glasses

Using inelastic x-ray scattering we studied the collective dynamics of the glassy alloy Ni33Zr67 in the first pseudo-Brillouin-zone, an energy-momentum region still unexplored in metallic glasses. We determine key properties such as the momentum transfer dependence of the sound velocity and of the acoustic damping, discussing the results in the general context of recently proposed pictures for acoustic dynamics in glasses. Specifically, we demonstrate the existence in this strong glass of well defined (in the Ioffe-Regel sense) acoustic-like excitations well above the boson peak energy.     

Real-time measurement of the orientational dynamics of aqueous solvation shells in bulk liquid water

We present a study of the orientational dynamics of aqueous solvation shells of halogenic anions in bulk water solution with femtosecond two-color midinfrared spectroscopy. These orientational dynamics have time constants between 2.5 and 12 ps, depending on the type of anion and the temperature. We find that the solvation shell of the larger ion I- shows faster dynamics than that of the smaller ions Cl- and Br-.     

Thermal conductivity and electrical resistivity of bulk indium and indium embedded in 7-nm channels of porous borosilicate glass

A “porous glass + indium” nanocomposite has been prepared. The thermal conductivity κ(T) and electrical resistivity ρ(T) of the nanocomposite have been measured in the temperature range 5–300 K, and their fractions accounted for by nanoindium embedded in 7-nm channels of the porous glass have been determined. For comparison, κ and ρ of the bulk polycrystalline indium sample have been measured in the same temperature range. The electronic and phonon components of the thermal conductivity have been calculated for the nanoindium and bulk indium. It has been demonstrated that, as the result of the emergence of boundary electron and phonon scattering in the nanoindium, the electrical resistivity of this material becomes larger, and the phonon thermal conductivity, smaller than those of the bulk indium.     

体超导铟对一维锌超导纳米线超导电性的抑制效应

文章细致研究了超导体铟/一维锌超导纳米线阵列/超导体铟夹心结构的超导电性.实验发现, 当锌纳米线的长度在２—６μm、直径等于40nm时,　宏观尺寸的超导体铟电极对中间的锌纳米线的超导电性具有反常的抑制作用. 即当铟处在超导态时, 中间的锌纳米线则停留在正常态. 如果施加一个磁场,使超导体铟电极变为正常态, 锌纳米线则恢复其超导电性. 这种奇异的现象与超导电极材料的类型及锌纳米线的直径和长度有关.     

体超导铟对一维锌超导纳米线超导电性的抑制效应

文章细致研究了超导体铟／一维锌超导纳米线阵列／超导体铟夹心结构的超导电性．实验发现，当锌纳米线的长度在2—6μm、直径等于40nm时，宏观尺寸的超导体铟电极对中间的锌纳米线的超导电性具有反常的抑制作用,即当铟处在超导态时，中间的锌纳米线则停留在正常态．如果施加一个磁场，使超导体铟电极变为正常态，锌纳米线则恢复其超导电性，这种奇异的现象与超导电极材料的类型及锌纳米线的直径和长度有关。     

Electron and phonon dynamics in indium antimonide crystals

Monte Carlo method is used for the study of electron and phonon dynamics in InSb crystals in the steady electric field. If the lattice temperature is significantly lower than the Debye temperature, and the lifetime of phonons is finite, their accumulation (especially LO ones) is found to occur in a limited range of momentum space. Accumulated phonons are shown to affect the values of electron drift velocity and mean energy. The values are subject to continuous increase in the time of ballistic flight upon step-like switching-on electric field, and subsequent decaying oscillations before accessing the stationary state. In contrast to these, the transient response of LO phonon number shows an abrupt increase after a picosdecond-scale delay, with a trend to subsequent saturation. Phonon band population inversion is discussed in relation to possible stimulated emission of photons.     

Magnetically stabilized electron-hole liquid in indium antimonide

Luminescence spectra of sufficiently pure n-type indium antimonide crystals (N _D−N _A=(1–22)·10¹⁴ cm⁻³) in a magnetic field of up to 56 kOe, at temperatures of 1.8–2 K, and high optical pumping densities (more than 100 W/cm²) have been studied. More evidence of the existence of electron-hole liquid stabilized by magnetic field has been obtained, and its basic thermodynamic parameters as functions of magnetic field have been measured. When the magnetic field increases from 23 to 55.2 kOe, the liquid density increases from 3.2·10¹⁵ to 6.7·10¹⁵ cm⁻³, the binding energy per electron-hole pair rises from 3.0 to 5.2 meV, and the binding energy with respect to the ground exciton level (work function of an exciton in the liquid) rises from 0.43 to 1.2 meV. Zh. éksp. Teor. Fiz. 111, 737–758 (February 1997)     

The direct pair correlation function of liquid indium

The static structure factor S(k) of liquid indium has been measured accurately down to $\text{k = 0.8}\text{A}\text{?}{}^{\mathrm{?1}}$ using CuKα radiation with reflection geometry. The direct pair correlation function in k space is analyzed to demonstrate the utility of this technique in reducing errors in the resulting direct pair correlation function in configuration space.     

Two-photon absorption and emission dynamics of bulk GaAs

Bulk n-type GaAs (dopant silicon) is investigated with picosecond pump pulses of a passively mode-locked Nd:glass laser. The two-photon absorption, the spontaneous emission, and the longitudinal amplified spontaneous emission are measured. The experimental results are compared with computer simulations and relevant material parameters are determined.     

Unconventional lattice dynamics in few-layer h-BN and indium iodide crystals

Unusual quadratic dispersion of flexural vibrational mode and red-shift of Raman shift of in-plane mode with increasing layer-number are quite common and interesting in low-dimensional materials, but their physical origins still remain open questions. Combining ab initio density functional theory calculations with the empirical force-constant model, we study the lattice dynamics of two typical two-dimensional(2 D) systems, few-layer h-BN and indium iodide(In I). We found that the unusual quadratic dispersion of flexural mode frequency on wave vector may be comprehended based on the competition between atomic interactions of different neighbors. Long-range interaction plays an essential role in determining the dynamic stability of the 2 D systems. The frequency red-shift of in-plane Raman-active mode from monolayer to bulk arises mainly from the reduced long-range interaction due to the increasing screening effect.     

Collective dynamics of Zr-based bulk metallic glasses

The collective dynamics for the longitudinal as well as the transverse modes of the phonon eigenfrequencies are carried out for three Zr-based bulk metallic glasses (BMGs) in the present paper by employing pseudopotential theory. The theoretical phonon models proposed by Hubbard-Beeby (HB), Takeno-Goda (TG) and Bhatia-Singh (BS) are used to generate the phonon dispersion curves (PDC). The elastic and thermodynamic properties have also been investigated for the said BMGs by using the elastic limit of the phonon dispersion curves. The screening impact was also observed by using five different forms of local field functions due to Hartree (H), Taylor (T), Ichimaru and Utsumi (IU), Faridet al. (F) and Sarkaret al. (S) for the aforesaid properties. The derived results are seen to be in qualitative agreement with the available experimental and theoretically calculated data, as they confirm the applicability of Shaw's constant core model potential and self-consistent phonon theory for such studies.     

液体体变弹性模量测量实验及研究

介绍了一种测量液体体变弹性模量的方法．同时研究了不同液体的密度、温度对液体体变弹性模量的影响．     

Effects of bulk diffusion on interfacial dynamics

We study the influence of bulk diffusion on the dynamics of an interface in the two-phase region of two component systems. We establish a set of equations of motion describing capillary waves and their coupling to a slow diffusion mode in the bulk. Valid for the general case of density dependent bulk diffusion coefficients, these equations are both non-local and non-linear. The nonlinearity is a realization of the full Galilean symmetry associated with the system. Studying the dispersion relations for the linear regime, we find a significant difference between systems with Ising symmetry and those without.     

High-frequency dielectric spectra from liquid crystals of series nCB and nOCB

The design of a resonant frequency-tunable high-sensitivity microstrip sensor is suggested. The permittivity dispersion of liquid crystals of two homologic series, alkylcyanobiphenyls (7CB and 8CB) and alkyloxycyanobiphenyls (7OCB and 8OCB), is studied at frequencies of 100–900 MHz. The dielectric spectra are shown to be the sum of the Debye relaxation and dielectric resonances observed at f≈160, 280, 360, 450, 550, and 650 MHz. The dielectric resonances are present in the spectra of all the samples in both the nematic and isotropic phase. The substitution of an oxygen atom (series nOCB) for a carbon atom (series nCB) in liquid crystal molecules has a minor effect on the dielectric resonance frequencies but changes the resonance intensities and splits some of the resonance lines.     

Short-pulse UV laser ablation of solid and liquid metals: indium

2 to 2.5 mJ/cm² when a 0.5 ps pulse is used instead of a 15 ns laser pulse. Measurements on liquid indium show a different behavior. With 15 ns laser pulses the threshold fluence is lowered by a factor of ∼3 from 100 mJ/cm² for solid indium to 30 mJ/cm² for liquid indium. In contrast, measurements with 0.5 ps laser pulses do not show any change in the ablation threshold and are independent of the phase of the metal at 2.5 mJ/cm². This behavior could be explained by thermal diffusion and heat conduction during the laser pulse and demonstrates in an independent way the energy lost into the material when long laser pulses are applied. Time-of-flight measurements to investigate the underlying ablation mechanism show thermal behavior of the ablated indium atoms for both ps and ns ablation and can be fitted to Maxwell-Boltzmann distributions. Received: 2 December 1996/Accepted: 11 December 1996     

Evolution of a reactive surface via subsurface defect dynamics

We find that the topography and composition of a reactive surface can evolve during epitaxy via motion of point and line defects within the material. We observe the response of a NiAl surface to an Al atom flux with low-energy electron microscopy. Initially, new NiAl layers grow as Al atoms exchange with bulk Ni atoms. When the surface is critically enriched in Al, condensation occurs at dislocations. They dissociate, move linearly, and leave tracks of altered composition and new atomic steps. We show how these dynamics depend on the identity and quantity of point defects near the surface.     

The high-temperature behaviour of gallium and indium liquid metal ion sources

Energy distribution diagrams and derived data are presented for gallium and indium liquid metal ion sources operated at elevated temperatures. Results for the gallium source confirm that a secondary peak is formed on the energy distribution diagram at source temperatures above 250°C. Contrary to the findings of other research workers, data presented here show that the indium source displays similar characteristics to that of gallium. Off-axis data are also given, showing that secondary peak formation is not limited to the centre of the beam. Present hypotheses propose that secondary peak formation is the result of an increased contribution to emission by free-space field ionisation at elevated temperatures. Data presented here for the gallium and indium sources are discussed and the above hypotheses are examined. It is concluded that a field ionisation mechanism does not satisfactorily explain the form of the high temperature liquid metal ion source energy distributions.     

High-frequency dynamics of Co/Fe multilayers with stripe domains

Within the framework of two-dimensional (2D) numerical micromagnetic simulations, the equilibrium magnetization configuration and the high-frequency (0.1–30 GHz) linear response of Co/Fe multilayers have been investigated in detail. Due to the perpendicular anisotropy of Co layers, a stripe domain pattern can develop through the whole multilayer, the characteristics of which depend on the magnitude of the perpendicular anisotropy, the respective thicknesses of Co and Fe layers and the number of Co/Fe bilayers in the stack. One of the most striking features associated with the layering effect is the ripening aspect of the static magnetization configuration across the multilayers which induces complicated dynamic susceptibility spectra including surface modes and volume modes strongly confined within the inner Fe layers. The effect of the cubic magnetocrystalline anisotropy of Fe layers and the influence of a nonuniform perpendicular magnetic anisotropy within the Co layers on the static and dynamic magnetic properties of Co/Fe multilayers are then analyzed quantitatively.