Ab initio molecular dynamics investigations of structural, electronic and dynamical properties of water in supercritical carbon dioxide

Ab initio molecular dynamics simulations of a solitary perdeuterated water molecule solvated in supercritical carbon dioxide have been performed along an isotherm at three different densities. Electron donor-acceptor interactions between the oxygen atom of water and the carbon atom of CO₂ as well as hydrogen bonded interactions between the two molecules have been shown to play a dominant role in the solvation. The mean dipole moment of the water molecule increases with the density of the solution, from a value of 1.85 D at low density to around 2.15 D at the highest density. The increase in the solvent density causes the water molecule to exhibit a range of behavior, from a free molecule to one that interacts strongly with CO₂. A blue shift in the bending mode of water has been observed with increasing solvent density. The carbon dioxide molecules which are present in the first neighbor shell of water are found to exhibit larger propensity to deviate from a linear geometry in their instantaneous configurations.      

Optical properties of pure and doped Y3Fe5O12 single crystals

Institute of Physics of Solids and Semiconductors, Academy of Sciences of Belarus, 17, P. Brovka Str., GSP, Minsk, 220072. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 63, No. 4, pp. 667–675, July–August, 1996.     

Optico-spectroscopic diagnostics of large-scale plasma clouds created above A surface under the action of A single-pulse laser in atmospheric-pressure air

To whom correspondence should be addressd.     

Optical properties of carbon nanotubes and BaTiO3 composite thin films

Multiwalled carbon nanotubes and BaTiO₃ composite films have been prepared by pulsed-laser deposition technique at room temperature and high temperature of 600℃, separately. The structures of the composite films are investigated by using scanning electron microscopy and x-ray diffraction. The optical behaviours of the samples produced at different temperatures are compared with Raman spectroscopy, and UV-visible absorption. And the observation by Z-scan technique reveals that the composite films have a larger optical nonlinearity, and the samples prepared at high temperatures have better transmittance and opposite sign imaginary part of optical third-order nonlinearity.     

多壁碳纳米管光限幅特性的研究

用化学气相沉积法制备了多壁碳纳米管,并将其溶解在甲苯溶液中.用波长为1064nm的皮秒脉冲激光测量该样品的透过率,发现了非常明显的光限幅特性.当入射光强较小时,透射光强度随入射光强度的增大而增大,输出与输入为线性关系;随着入射光强的增大,透射光强增长的速度明显变慢,并逐渐趋于饱和.当入射光强度较小时,样品的透过率接近100%;而当入射光强为8GW/cm²时,非线性透过率达到30%.根据三光子吸收理论计算,理论拟合与实验结果非常符合,说明多壁碳纳米管的三光子吸收产生了光限幅效应.实验测 关键词： 多壁碳纳米管 光限幅 三光子吸收     

Pb1－xMnxSe薄膜的光学特性

采用分子束外延的方法在BaF₂(111)衬底上制备出了高质量的Pb_1-xMn_xSe(0≤x≤0.0681)薄膜.X射线衍射结果表明，Pb₁-xMn_xSe薄膜为立方相NaCl型结构，没有观察到MnSe相分离现象，薄膜的取向为平行于衬底(111)晶面.晶格常数随着Mn含量的增加逐渐减小，Mn含量由Vegard公式得到.通 关键词： 1-xMn_xSe外延薄膜')" href="#">Pb_1-xMn_xSe外延薄膜 透射光谱 带隙 折射率     

The thermal conductivity of argon,carbon dioxide and nitrous oxide

The paper presents new, absolute measurements of the thermal conductivity of three gases: argon (Ar), carbon dioxide (CO₂) and nitrous oxide (N₂O). The measurements have been carried out with a transient hot-wire instrument in the temperature range 308 to 430 K and at pressures up to 11 MPa. For most of the range of thermodynamic states covered by the measurements it is estimated that the accuracy of the thermal conductivity data is one of ±0.3%. However, for carbon dioxide and nitrous oxide near their critical conditions the accuracy is degraded and the uncertainty may be as much as ±2%. The new experimental data for argon confirm the accuracy claimed for the thermal conductivity in the limit of zero-density.The thermal conductivity of the polyatomic gases in the limit of zero-density is used in conjunction with information on other transport cross-sections for the same systems, to extract a consistent set of cross-sections sensitive to the anisotropy of the intermolecular pair potential for use in the testing of proposed potential surfaces. Cross-sections for both of the available formulations of the thermal conductivity of a polyatomic gas due to Wang Chang and Uhlenbeck and Thijsse et al. are derived. For both gases it is shown that the Mason-Monchick approximation breaks down in either formulation. However, the effect of the failure on the formulation of Thijsse et al. is smaller and it is possible to represent the data with the aid of a single cross-section which has a very simple temperature dependence. The analysis also demonstrates that all available high-temperature thermal conductivity data for carbon dioxide are in substantial error.In the moderately dense gas the concept of a temperature-independent excess thermal conductivity is confirmed to a high degree of precision for carbon dioxide and argon when due allowance is made for the critical enhancement. A generalized correlation of the temperature dependence of the first density coefficient of thermal conductivity is broadly confirmed.     

Monte Carlo simulation of carbon monoxide,carbon dioxide and methane adsorption on activated carbon

In this study, the adsorption capacity of pure and activated carbon with regard to carbon monoxide (CO), carbon dioxide (CO₂) and methane (CH₄) gases at 298?K and pressure from 0.01 up to 2.0?MPa has been investigated computationally. Computational work refers to Monte Carlo (MC) simulation of each adsorbed gas on a graphite model with varying density of activation sites. The Grand Canonical Monte Carlo (GCMC) simulation technique was employed to obtain the uptake of each adsorbed gas by considering a graphite model of parallel sheets activated by carboxyl and hydroxyl groups, as observed experimentally. The simulation adsorption data for these gases within the examined carbon pore material are presented and discussed in terms of the adsorbate fluid molecular characteristics and corresponding interactions between adsorbate species and adsorbent material. We found that the simulated adsorption uptake of the examined graphite model under these conditions with regard to the aforementioned fluids increases in the order CO?<?CH₄?<?CO₂.     

Interactions of charged dust particles in clouds of charges

Two charged dust particles inside a cloud of charges are considered as Debye atoms forming a Debye molecule. Cassini coordinates are used for the numerical solution of the Poisson-Boltzmann equation for the charged cloud. The electric force acting on a dust particle by the other dust particle was determined by integrating the electrostatic pressure on the surface of the dust particle. It is shown that attractive forces appear when the following two conditions are satisfied. First, the average distance between dust particles should be approximately equal to two Debye radii. Second, attraction takes place when similar charges are concentrated predominantly on the dust particles. If the particles carry a small fraction of total charge of the same polarity, repulsion between the particles takes place at all distances. We apply our results to the experiments with thermoemission plasma and to the experiments with nuclear-pumped plasma.     

Effect of synthesis conditions protective and decorative titanium nitride coatings on their optical and color parameters

Optical and color parameters of titanium nitride coatings deposited from an unseparated vacuum-arc plasma flux and a flux which is separated from macroparticles are culculated in varying sputtering regimes. Physics and Engineering Institute, National Academy of Sciences of Belarus, 4, Zhodinskaya St., Minsk, 220141. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 1, pp. 87–94, January–February, 1998.     

Luminescent properties of chromates of alkali metals

T. Shevchenko Kiev State University, 6, Acad. Glushkov Ave., Kiev, 252127, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 3, pp. 239–248, May–June, 1995.