The synthesis and characterization of bis(phtha1ocyaninato)lutetium (Pc2Lu) and lithium phthalocyanine (PcLi) substituted with long alkyl chains are reported. They form columnar liquid crystals over an extended domain of temperature. Oxidation of the lutetium derivative to the corresponding ionic compound (s-Pc2Lu)',BF; leads to a more stable mesophase. The magnetic properties of (S-PC)~LU are determined by electron paramagnetic resonance (EPR) spectra demonstrating the influence of the disorder on the EPR line width. Electrical properties of the solid and liquid crystalline phases have been measured in the frequency range lO-'-lOS Hz. The intracolumnar order is shown to determine the frequency dependence of the conductivity:for the disordered columnar liquid crystalline phase and u0,j for the corresponding ordered one.
The positron distribution of charge along the (1 11) direction is calculated for elemental and compound semiconductors. The results show that the positron has a strong affinity for one sort of atom in binary semiconductors. This relative positron affinity may lead to the positron preferentially annihilating with the electrons of that sort of atom in compound semiconductors. The trends in going from Ge to CdTe through GaAs show an increase in positron affinity for the anion over the cation.La densite de charge des positrons a Btk calculee suivant la direction (1 11) pour des semiconducteurs simples et composes. Les resultats montrent que le positron a une grande affinite pour un type d'atome dans les semiconducteurs binaires. Cette affinite relative peut amener le positron a s'annihiler de preference avec les electrons de ce type d'atome du compose. La densitt de charge calculee pour plusieurs semicondbcteurs, de Ge a CdTe en passant par GaAs, montre une affinite du positron croissante pour l'anion plutBt que pour le cation.
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