Structural, energetic, and electronic properties of Sin, Gen, and SinGen clusters

Results of a theoretical study of the properties of Si_n, Ge_n, and Si_nGe_n clusters are presented. An approximate density-functional method in combination with genetic algorithms have been used in an unbiased determination of the structures of the lowest total energy. The resulting structural, energetic, and electronic properties are analysed and compared with each other for the different systems.     

Mesomorphic, dielectric, and optical properties of fluorosubstituted biphenyls, terphenyls, and quaterphenyls

Compounds with moderate and large negative dielectric anisotropy (Δɛ) are very attractive liquid crystal (LC) for vertical alignment mode (VA). Materials with such properties can be achieved by lateral substitution of a polar group into a mesogenic molecule. We synthesized some new LC materials with a negative value of Δɛ, a moderately high birefringence (Δn), and a low viscosity. The mesomorphic and physical behaviour of the novel biphenyls, terphenyls and quaterphenyls fluorosubstituted in the rigid core and also with fluorinated alkyl and alkoxy chains are investigated. The prepared series of four LC compounds are promising for new LC mixtures for various applications. Examples of nematic mixtures with Δɛ∼−3.25 will be presented.     

Cointegration of output, capital, labor, and energy

Cointegration analysis is applied to the linear combinations of the time series of (the logarithms of) output, capital, labor, and energy for Germany, Japan, and the USA since 1960. The computed cointegration vectors represent the output elasticities of the aggregate energy-dependent Cobb-Douglas function. The output elasticities give the economic weights of the production factors capital, labor, and energy. We find that they are for labor much smaller and for energy much larger than the cost shares of these factors. In standard economic theory output elasticities equal cost shares. Our heterodox findings support results obtained with LINEX production functions.     

Solution absorption and luminescence studies of tetraphenylboron, -carbon, -silicon, -germanium, -tin, -lead, -phosphorus, -arsenic,and -antimony

The lowest absorption band of the tetraphenyl compounds resembles that of the lowest absorption band of benzene with the following difference. In benzene the electronic origin is strictly forbidden, and all intensity is associated with a symmetric progression built on one mode of asymmetric vibration. In the tetraphenyl compounds the intensity associated with the asymmetric vibration is relatively unaffected; however, there is increasing intensity associated with the electronic origin and a symmetric progression built on it along the series

$\text{φ}{}_4\text{Pb}\text{< φ}{}_4\text{Sn}\text{< φ}{}_4\text{Ge}\text{< φ}{}_4\text{Si}\text{< φ}{}_4\text{C}\text{? φ}{}_4\text{B}{}^{\mathrm{?}}\text{< φ}{}_4\text{Sb}{}^{\mathrm{+}}\text{< φ}{}_4\text{As}{}^{\mathrm{+}}\text{< φ}{}_4\text{P}{}^{\mathrm{+}}$

. For the cations it is the electronic origin and the progression built on it that are the primary source of intensity. This effect is attributed to an inductive perturbation. A similar effect is observed in the fluorescence spectrum. In phosphorescence, the relative enhancement of the electronic origin and the progression built on it is far less marked. The phosphorescence emission of φ₄Pb and φ₄Sb⁺ are red shifted from the others by ～0.5 eV, an effect attributed to formation of a triplet excimer. Increasing spin-orbit coupling in the triplet due to a heavy atom effect can be seen in the decreasing phosphorescence lifetime (range 4 sec to 4 msec) and decreasing ratio of $\text{φ}{}_{\mathrm{f}}\text{φ}{}_{\mathrm{p}}$ (fluorescence to phosphorescence quantum yields) in the order

$\text{φ}{}_4\text{C}\text{> φ}{}_4\text{B}\text{> φ}{}_4\text{Si}\text{> φ}{}_4\text{P}{}^{\mathrm{+}}\text{> φ}{}_4\text{Ge}\text{> φ}{}_4\text{As}{}^{\mathrm{+}}\text{> φ}{}_4\text{Sn}$

In all cases nonexponential decay of phosphorescence is observed.     

Fabrication,Microstructure, and Properties of Nanoporous Pd,Ni, and Their Alloys by Dealloying

Nanoporous metals can be fabricated by dealloying, which is one of the reactions that occur during the corrosion of alloys. Nanoporous gold has been widely investigated for several decades, and it has recently been found that other metals, such as platinum, palladium, nickel, and copper, can form nanoporous structures through the dealloying of binary alloys. This article mainly shows fabrication and properties of nanoporous palladium and nickel after introduction of nanoporous metals by referring to nanoporous gold as an example. It is necessary to select binary alloys with suitable elements, in which the dissolution of the less noble element and the aggregation of the nobler element at the solid/electrolyte interface are simultaneously allowed. Postprocessing by thermal or acid treatment alters the nanoporous structure. Various properties of nanoporous metals (including mechanical, catalytic, piezoelectric, hydrogenation, and magnetic ones) are different from those of bulk and nanocrystalline materials and nanoparticles because of their specific three-dimensional network structures consisting of nanosized pores and ligaments. Hydrogenation and magnetic properties are reviewed in terms of lattice strain at curved surfaces. These new metallic nanomaterials are now being investigated from the viewpoint of functional applications, and provide much room for study in various fields.     

Sonochemical synthesis of carbon dots,mechanism, effect of parameters,and catalytic,energy, biomedical and tissue engineering applications

Carbon-based nanomaterials are gaining more and more interest because of their wide range of applications. Carbon dots (CDs) have shown exclusive interest due to unique and novel physicochemical, optical, electrical, and biological properties. Since their discovery, CDs became a promising material for wide range of research applications from energy to biomedical and tissue engineering applications. At same time several new methods have been developed for the synthesis of CDs. Compared to many of these methods, the sonochemical preparation is a green method with advantages such as facile, mild experimental conditions, green energy sources, and feasibility to formulate CDs and doped CDs with controlled physicochemical properties and lower toxicity. In the last five years, the sonochemically synthesized CDs were extensively studied in a wide range of applications. In this review, we discussed the sonochemical assisted synthesis of CDs, doped CDs and their nanocomposites. In addition to the synthetic route, we will discuss the effect of various experimental parameters on the physicochemical properties of CDs; and their applications in different research areas such as bioimaging, drug delivery, catalysis, antibacterial, polymerization, neural tissue engineering, dye absorption, ointments, electronic devices, lithium ion batteries, and supercapacitors. This review concludes with further research directions to be explored for the applications of sonochemical synthesized CDs.     

Intrinsic and Zn-, Ce-, Tb-, Er-, Sm-, and Eu-Activated photoluminescence of pseudoamorphous GaN and InGaN thin films

Thin films of pseudoamorphous GaN (a-nc-GaN), as well as of its alloys with indium, In_xGa_1−x N (x=0.04, 0.16), were prepared by magnetron sputtering of a metallic target in the plasma of a reactive nitrogen and argon mixture. The a-nc-GaN films were codoped by the Zn acceptor impurity and a set of rare-earth metal (REM) dopants, namely, Ce, Tb, Er, Sm, and Eu. Photoluminescence (PL) spectra excited by a nitrogen laser with wavelength λ=337 nm at room temperature and 77 K were measured for all compositions and a set of impurities. It was shown that the high-energy PL edge of the pseudoamorphous (a-nc) GaN matrix lies at the same energy as that of the crystalline (epitaxial) c-GaN. As in c-GaN, the Zn acceptor impurity stimulates blue luminescence; however, the PL spectrum is substantially more diffuse, with practically no temperature quenching of the PL present. Indium doping in an amount of 16 at. % results in strong PL with a diffuse peak at 2.1–2.2 eV; the PL of the alloy exhibits temperature quenching as high as a factor of three to four in the interval 77–300 K. The decay time of the PL response increases up to 50 μs. RE impurities enter the amorphous GaN host as trivalent ions and produce narrow-band (except Ce) high-intensity spectra, thus indicating both a high solubility of RE impurities in a-nc-GaN and the generation of an effective crystal field (by the GaN anion sublattice) whose local symmetry makes the intracenter f-f transitions partly allowed. __________ Translated from Fizika Tverdogo Tela, Vol. 45, No. 3, 2003, pp. 395–402. Original Russian Text Copyright ? 2003 by Andreev.     

Density functional theory study of structural,electronic,and thermal properties of Pt,Pd, Rh,Ir, Os and PtPdX(X= Ir,Os, and Rh) alloys

The structural, electronic, mechanical, and thermal properties of Pt, Pd, Rh, Ir, Os metals and their alloys Pt Pd X(X= Ir, Os and Rh) are studied systematically using ab initio density functional theory. The groundstate properties such as lattice constant and bulk modulus are calculated to find the equilibrium atomic position for stable alloys. The electronic band structure and density of states are calculated to study the electronic behavior of metals on making their alloys. The electronic properties substantiate the metallic behavior for all studied materials. The firstprinciples density functional perturbation theory as implemented in quasi-harmonic approximation is used for the calculations of thermal properties.We have calculated the thermal properties such as the Debye temperature, vibrational energy, entropy and constant-volume specific heat. The calculated properties are compared with the previously reported experimental and theoretical data for metals and are found to be in good agreement. Calculated results for alloys could not be compared because there is no data available in the literature with such alloy composition.     

中老年高血压患者血清中钾钠钙镁锌铜铁锰的含量分析

用原子吸收法对 4 8名高血压患者和 5 2名正常健康人进行血清中K ,Na ,Ca ,Mg ,Zn ,Cu ,Fe和Mn的测定。结果表明 ,患高血压组血清中Na ,Mg ,Zn ,Fe和Mn的水平含量均高于健康对照组 ,K ,Ca和Cu的水平含量均低于健康对照组。患高血压组血清Na/K比值均高于健康对照组 ,Ca/Mg ,Cu/Zn比值均低于健康对照组。建议 ,患者适当增补人体内K ,Ca,Mg和Cu的含量 ,减少Na的过多摄入 ,科学地控制Zn ,Fe和Mn的增加 ;注意体内Na/K ,Ca/Mg和Cu/Zn比值的平衡关系 ,降低Na/K比 ,提高Cu/Zn比 ,补Ca的同时一定要注意适当补充Mg ,有利于高血压病的预防和治疗。     

Equations of state for copper,silver, gold,aluminum, nickel,and lead

Semiempirical equations of state are obtained for copper, silver, gold, lead, nickel, and aluminum, which permit a study of the mechanical properties of the crystalline lattices of these metals when subjected to a complex system of stresses over the entire elastic deformation region, and lead to an evaluation of the mechanical destruction parameters of these lattices. As an example, the case of omnidirectional tension is examined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 66–70, January, 1973.     

Density-functional calculations of alpha, beta, gamma, delta, delta', and epsilon plutonium

Total energies for the six known polymorphs of plutonium metal have been calculated within spin and orbital polarized density-functional theory as a function of lattice constant. Theoretical equilibrium volumes and bulk moduli correspond well with experimental data and the calculated total energies are consistent with the known phase diagram of Pu. It is shown that a preference for the formation of magnetic moments, increasing through the alpha-->beta-->gamma phases, explains their position in the ambient pressure phase diagram and their anomalous variation of atomic density. A simple model is presented that establishes a relationship between atomic density, crystal symmetry, and magnetic moments which is universally valid for all Pu phases.     

Simple fundamental equation of state for liquid,gas, and fluid of argon,nitrogen, and carbon dioxide

A new fundamental low-parametric equation of state in the form of reduced Helmholtz function for describing thermodynamic properties of normal substances was obtained using the methods and approaches developed earlier by the authors. It allows us to describe the thermal properties of gas, liquid, and fluid in the range from the density in ideal-gas state to the density at a triple point (except the critical region) with sufficiently high accuracy close to the accuracy of experiment. The caloric properties and sound velocity of argon, nitrogen, and carbon dioxide are calculated without involving any caloric data, except the ideal gas enthalpy. The obtained values of isochoric heat capacity, sound velocity, and other thermodynamic properties are in good agreement with experimental (reliable tabular) data.     

Alpha particle and deuteron impactL-shell ionization of Ar,Cu, Ge,Br, Zr and Ag

Alpha particle and deuteron impactL-subshell ionization cross-sections of Ar, Cu, Ge, Br, Zr and Ag have been computed using Vriens’ expressions for ionization cross-section of atoms due to impact of heavy charged particles. The effects of Coulomb deflection of the projectile and increase in binding of the target electron in the presence of projectile have been incorporated. Hartree-Fock velocity distributions for the target electrons have been used in the present calculations. The simple binary encounter approximation model is found to give results which are in satisfactory agreement with those obtained from experiments and from other theories.     

Beta-decay energies and masses of short-lived isotopes of rubidium,caesium, francium,and radium

Total decay energies have been measured for a number of neutron-deficient Rb and Cs isotopes, as well as for some neutron-rich isotopes of Fr and Ra. Mass separated sources were produced at the ISOLDE on-line separator at CERN. By applying two differentβ-γ coincidence methods,Q values or their lower limits were determined for^76–78Rb,⁸⁰Rb,^121–124Cs,²²²Fr,^224–226Fr,²²⁹Ra-²²⁹Ac. For many of these nuclei, the atomic mass excesses could be derived, allowing the comparison of masses of far unstable nuclei with predictions from mass formulae. The odd-odd nuclei⁷⁶Rb and⁷⁸Rb appear to be 1?1 1/2 MeV more strongly bound than expected from the systematics.     

Optical homogeneity,defects, and photorefractive properties of stoichiometric,congruent, and zinc-doped lithium niobate crystals

Using the laser-conoscopy method, the photorefractive light-scattering method, and the Raman light-scattering method, we have studied the structural and optical homogeneities and photorefractive properties of (i) stoichiometric lithium niobate crystals (LiNbO₃(stoich)), which were grown from a melt with 58.6 mol % of Li₂O; (ii) congruent crystals (LiNbO₃(congr)); and (iii) congruent crystals that were doped with Zn²⁺ cations (LiNbO₃:Zn; [Zn] = 0.03–1.59 mol %). We have shown that the speckle-structure of the photorefractive light scattering in all the crystals is three-layer. The shapes of the second and third layers repeat in general the shape of the first layer. We have shown that the differences that are observed between the Raman spectra, the photorefractive light scattering, and the conoscopic patterns of the examined crystals are caused by the fact that defects are distributed inhomogeneously over the volume of these crystals and that Zn²⁺ cations are incorporated inhomogeneously into the lattice. This leads to the appearance of local changes in the elastic characteristics of the crystal and to the appearance of mechanical stresses, which locally change the optical indicatrix and, correspondingly, the conoscopic pattern and the Raman spectrum.     

Diffusion of sodium,potassium, calcium,manganese, and radon in tuff and clinoptilolite under leaching

Nuclear physics methods are used to determine the diffusion coefficients of Na, Ca, Mn, K, and ²²²Rn in clinoptilolite (Sokirnitsa occurrence, Ukraine) and in natural tuff (Yucca Mountain, Nevada, United States) and in tuff irradiated by γ-quanta (E _max = 23 MeV) to a dose of 10⁷ Gy at a leaching temperature of 37°C. The diffusion coefficients of sodium and potassium in clinoptilolite are found to differ considerably: 4 × 10⁻¹⁷ and 2 × 10⁻²⁰ m²/s, respectively. This indicates the influence of aquacomplexes on the cation transfer. The diffusion coefficient of radon in these materials is determined: in clinoptilolite it equals 2.5 × 10⁻¹² m²/s.     

Elements of Iso-, Geno-, Hyper-Mathematics for Matter, Their Isoduals for Antimatter, and Their Applications in Physics, Chemistry, and Biology

Pre-existing mathematical formulations are generally used for the treatment of new scientific problems. In this note we show that the construction of mathematical structures from open physical, chemical, and biological problems leads to new intriguing mathematics of increasing complexity called iso-, geno-, and hyper-mathematics for the treatment of matter in reversible, irreversible, and multi-valued conditions, respectively, plus anti-isomorphic images called isodual mathematics for the treatment of antimatter. These novel mathematics are based on the lifting of the multiplicative unit of ordinary fields (with characteristic zero) from its traditional value +1 into: (1) invertible, Hermitean, and single-valued units for isomathematics; (2) invertible, non-Hermitean, and single-valued units for genomathematics; and (3) invertible, non-Hermitean, and multi-valued units for hypermathematics; with corresponding liftings of the conventional associative product and consequential lifting of all branches of mathematics admitting a (left and right) multiplicative unit. An anti-Hermitean conjugation applied to the totality of quantities and their operation of the preceding mathematics characterizes the isodual mathematics. Intriguingly, the emerging formulations preserve the abstract axioms of conventional mathematics (that based on the unit +1). As such, the new formulations result to be new realizations of existing abstract mathematical axioms. We then show that the above mathematical advances permit corresponding liftings of conventional classical and quantum theories with a resolution of basic open problems in physics, chemistry, and biology, numerous experimental verifications, as well as new industrial applications.     

Highlights of Supersymmetry, Superstrings, and M-Theory

The present lecture is a beginer's guide to supersymmetry, superstrings, and M-theory. It addresses students and scientists whose basic research topic in theoretical physics is a different one but who, nonetheless, wish to gain a glimpse into this exciting new field of theoretical physics.     

Heat capacity of rare-earth cuprates,orthovanadates, and aluminum garnets,gallium garnets,and iron garnets

Physics of the Solid State - The correlation between the heat capacities of rare-earth cuprates, orthovanadates, and garnets with ionic radius R 3+ has been analyzed. It has been shown that the...     

Structural stability and structural imitation of (M = Mn,Mo, Nb,Ti, V,Al, Cr,Ni and Si)

The structural stability of La₂Co_17-xM_x (M = Mn, Mo, Nb, Ti, V, Al, Cr, Ni and Si) based on the interatomic potential has been studied. The calculated site preference of the third element M is found to be the 6c site, which is in agreement with the experiments. In the calculations, if the crystal cohesive energy of La₂Co₁₆Mn is taken as the highest one in the crystallization of La₂Co_17-xM_x, the lowest content x of the third element M (M = Mn, Mo, Nb, Ti and V) required to stabilize La₂Co_17-xM_x, is near that found in the experiments. The differences of the cell parameters between the calculated and the experimental values are less than 0.4%. The differences of the atomic parameters for Co (or M) between the calculated and the experimental values are about or even smaller than 1%, and that of La is about 3%. Because the energies of La(Co_1-xAl_x)₁₃ are lower than those of La₂(Co_1-xAl_x)₁₇, La₂(Co_1-xAl_x)₁₇ could not be formed in the experiments. In the calculations, with either a range of deformation of the structure or the reconstruction of the initial structure La₂Co₁₇ from LaCo₅, the same results including the cohesive energy curves and the crystallographic parameters can be retrieved after the action of the interatomic potentials. Received 1st November 2002 / Received in final form 17 February 2003 Published online 23 May 2003 RID="a" ID="a"e-mail: hchang@aphy.iphy.ac.cn