Thomas–Fermi theory from a perturbative treatment of the hydrogenic limit energy density functional: A possible link to local density functional theory

A perturbation expansion which connects the hydrogenic limit energy density functional to the Thomas–Fermi functional is discussed. This perturbation series, where the Coulomb energy density functional is treated as the perturbation to the hydrogenic limit functional, is, in fact, the q = (N/Z) expansion of Thomas–Fermi theory. A truncated form of the first-order correction to the functional provides further insight into the model which treats the ground state energy as a local functional of the electron density.     

Dipole Cauchy moments of the atoms H through Ar

Summary Dipole Cauchy moments of the atoms through Ar are calculated using the hydrodynamic formulation of time-dependent Kohn-Sham theory. The exchange-correlation energy density functional is approximated by the gradient expansion for atoms. Using variational trial functions that contain both linear and nonlinear variational parameters, we are able to reproduce (to three or four significant figures) the static dipole polarizabilities obtained by explicitly solving the relevant differential equations. The resulting dipole Cauchy moments provide a convenient starting point for calculating other properties which result from the linear interaction of atoms with a time varying electric field.     

An example where orbital relaxation is an important contribution to the Fukui function

Density-functional electronic structure calculations are performed on the molecules Cr2(hpp)4, Mo2(hpp)4, and W2(hpp)4, where the bridging ligand, hpp, is the anion of 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine. The calculated electronic densities are used to determine the Fukui functions. These molecules are unique not only in their ability as electron donors but also because orbital relaxation plays a decisive role in their reactivity. Unlike other examples in the literature, the reactivity of these compounds cannot be expressed solely in terms of the highest occupied and lowest unoccupied Kohn-Sham orbitals but only using the Fukui function, which includes the effects of orbital relaxation.     

p-type ZnO thin films grown by RF plasma beam assisted Pulsed Laser Deposition

The high exciton binding energy and band gap energy of ZnO thin films open the prospect of fabricating semiconductor lasers in the ultraviolet spectral range. A prerequisite for laser diode fabrication is highly p-doped ZnO which was not reproducibly obtained up to now. Without intentional doping ZnO exhibits n-type conduction. ZnO thin films have been obtained by radio-frequency assisted pulsed laser deposition. A metallic Zn target was used for ablation in an oxygen and nitrogen RF discharge. The electrical and morphological properties of the films grown on Si were studied by Atomic Force Microscopy (AFM), X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), optical absorption and Hall Effect measurements for different ratios between the nitrogen and oxygen content. The AFM images of the as-grown ZnO films reveal high quality surfaces with low values for the surface roughness and a sharp distribution of grains sizes as an effect of the RF discharge. The XRD patterns for all samples exhibit only (002) and (004) peaks indicating that the c-axis is always oriented normal to the substrate surface. The films present p-type conductivity with different carrier concentration and mobility depending on the nitrogen/oxygen ratio.     

4-Trichloroacetyl-1,2,3-triazoles: A versatile building block for rapid assessment of carbohydrazides and rufinamide derivatives

This work reports the synthesis of a series of (1H-1,2,3-triazol-4-yl)carbohydrazides (2), which were obtained from 4-trichloroacetyl-1H-1,2,3-triazoles (1). Triazoles 1 were synthesized by 1,3-dipolar cycloaddition reaction, starting from 4-alkoxy-1,1,1-trichloroalk-3-en-2-ones and benzyl azides and easily (15 min) converted to 2 by reaction with hydrazine hydrate (73–82% yield). Carbohydrazides 2 proved to be a versatile building block for constructing a series of fluorinated heterocycles analogous to rufinamide, i.e., 1H-1,2,3-triazol-4-yl-1,3,4-oxadiazoles, a pyrrole derivative, and a 2-pyrazoline, through [4+1]–, [1+4]–, and [3+2]–cyclocondensation reactions, respectively. Finally, and according to the Lipinski’s rule of five, 2,6-difluorobenzylated 1,2,3-triazoles can be considered as potential candidates for further biological activity assays.     

Methyl hydrogen peroxide dimer: A structural study

Methyl hydrogen peroxide (MHP) exhibits a tendency to form a stable dimer by hydrogen-bonding. Ab initio theoretical investigations on methyl hydrogen peroxide dimer (MHPD) carried out herein lead to several energetically stable structures that have a direct bearing on the reactivity of the monomer in terms of its molecular electrostatic potential (MESP). To gauge the role played by the electron-correlation in lending stability to MHP and its dimer, we employ the density functional theory (DFT) (as implemented by B3LYP-functional), and subsequently second order Møller-Plesset (MP2) perturbation theory, using the basis sets 6-31G(d, p) and 6-311++G(2d, 2p). Simulated infra-red vibrational spectra lead to spectral intensity redistribution upon dimerization. Energetically the lowest MHPD is endowed with inversion symmetry and has two hydrogen bonds, while three other structures emerge: one energetically very close with two H-bonds, and the two others, with three H-bonds each, yet higher by about 2 kcal mol⁻¹.     

Effect of nanoparticles on the interfacial properties of liquid/liquid and liquid/air surface layers

An investigation is reported on the interfacial properties of nanometric colloidal silica dispersions in the presence of a cationic surfactant. These properties are the result of different phenomena such as the particle attachment at the interface and the surfactant adsorption at the liquid and at the particle interfaces. Since the latter strongly influences the hydrophobicity/lipophilicity of the particle, i.e., the particle affinity for the fluid interfacial environment, all those phenomena are closely correlated. The equilibrium and dynamic interfacial tensions of the liquid/air and liquid/oil interfaces have been measured as a function of the surfactant and particle concentration. The interfacial rheology of the same systems has been also investigated by measuring the dilational viscoelasticity as a function of the area perturbation frequency. These results are then crossed with the values of the surfactant adsorption on the silica particles, indirectly estimated through experiments based on the centrifugation of the dispersions. In this way it has been possible to point out the mechanisms determining the observed kinetic and equilibrium features. In particular, an important role in the mixed particle-surfactant layer reorganization is played by the Brownian transport of particles from the bulk to the interface and by the surfactant redistribution between the particle and fluid interface.     

Properties and structure of interfacial layers formed by hydrophilic silica dispersions and palmitic acid

The properties and structure of different types of interfacial layers obtained from aqueous dispersions of nanometric silica and palmitic acid (PA) have been studied and characterized by different diagnostics and measurements. The investigations concern PA monolayers spread on the silica dispersions, dispersions in contact with PA solutions in oil and silica dispersions containing PA, aiming at elucidating the role of the PA interaction with the particles and investigating the surface-activity of the originated silica-PA complexes. Drop shape tensiometry was utilized to measure the dynamic surface and interfacial tension while a Langmuir trough apparatus was used to obtain compression isotherms of the spread PA layers and to measure the dilational viscoelasticity according to the oscillating barrier method. Brewster angle microscopy and ellipsometry were utilized to investigate the lateral and vertical structure of the interfacial layers. From this multifold approach emerges a complex picture of the features of these interfacial layers that can be rationalized on the basis of the adsorption of PA on the particle surface. The results evidence a threshold in PA adsorption above which particles change from hydrophilic to partially hydrophobic, promoting their incorporation into the interfacial layer.     

Finite groups and subgroup-permutability

Subgrouppermutability in a finite group is studied, in order to distinguish between irreducible and reducible groups and to give a bound for the diameter. A simple nonabelian finite group is irreducible and its diameter is less or equal16 while a reducible group is forced to be soluble and the bound of the diameter of such a group is 4.Research partially supported by G.N.S.A.G.A. of C.N.R. and M.U.R.S.T. of Italy.