Polypropylene–MAlN (M = Ti,Cr) interface interactions

We have studied the influence of transition metal (M = Ti, Cr) and nonmetal (N, O) valence electron concentration, surface defects, and radicals on the interaction of polypropylene and cubic M_0.5Al_0.5N (002) and (111) surfaces using ab initio calculations. For the ideal and defected surface, the work of separation is low and not affected by valence electron concentration, implying weak interactions. Striking differences occur for radicals, where an increase by two orders of magnitude is observed. This may be understood based on the electronic structure. Radicals give rise to strong bonding across the interface and hence strong interactions.     

Origin of the nitrogen over- and understoichiometry in Ti(0.5)Al(0.5)N thin films

To identify the origin of the experimentally observed nitrogen over- and understoichiometry in TiAlN thin films, various point defect configurations were studied by ab initio calculations in terms of formation energies, equilibrium volume and elastic moduli. From formation energies and comparison to existing experimental equilibrium volume and elasticity data, it is shown that nitrogen vacancies and metal vacancies are responsible for nitrogen understoichiometry and overstoichiometry, respectively. Irrespective of the type of vacancies, the bulk modulus is decreased by approximately 7% as the nitrogen concentration is increased or decreased by 3 at.%.     

Untersuchung von Getreide, Mehl und Backwaren

Ohne Zusammenfassung     

The molecular structure of cis- and trans-bicyclo [4.2.0]-octane in the gas phase as studied by electron diffraction and molecular mechanics

The molecular structure of Cis- and trans-bicyclo[4.2.0]octane in the gas phase was studied. Molecular mechanics calculations applying Boyd's force Held were used for constraining differences between structural parameters during least squares analysis and for calculating vibrational amplitudes. The cyclohexane ring was found to have a distorted chair conformation, the ring in the cis isomer being flattened along the junction and more twisted in the other part. For the trans compound the reverse is true. The following structural parameters were obtained (r_a-structure):cis: r(C-C)_av. = 1.535 Å. Cyclohexane ring: average bond angle 112.9°; average torsional angle 48°. Cyclobutane ring: average bond angle 88.9°; puckering 157°. The dihedral angle between the bisecting planes of the C(2)-C(1)-C(6)-C(5) and C(8)-C(1)-C(6)-C(7) torsional angles, is 119° - the “connection angle” of the two rings.trans: r(C-C)_av.= 1.532 Å. Cyclohexane ring: average bond angle 110.4° ; average torsional angle 57°. Cyclobutane ring: average bond angle 87.3°; puckering 145°. The “connection angle” is 180° (C₂ symmetry).Comparison is made with structures of related compounds.