Directional property rhombohedral

In this work we perform an investigation of cooperative static in the monoclinic phase and dynamic in rhombohedral JT effect of pure LaMn03 using pair interionic potentials in shell model approximation with the direct inclusion of the JT term in crystal energy and dynamic matrix of a crystal. The magnetic and RS properties of the rhombohedral LaMn03 are simulated in the framework of the cooperative dynamical effect approximation. 

The Bi2Te3 compound is the most excellent material for thermoelectric cooling materials at around room temperature, and has been widely used in the precise temperature control machines etc. The compound has a layered rhombohedral structure. Then the compound has strong anisotropies on mechanical and thermoelectric properties. The properties vertical to the direction of c-axis are better than parallel[l]. Anisotropy of... 

If the local structure deviates from the average structure, the crystal symmetry is usually broken and the symmetry is lowered. For instance, the local symmetry may be rhombohedral or tetragonal but if the direction of the axes vary randomly from site to site, the system would appear cubic as a whole. Then, even though the crystal structure is cubic, the solid would have many properties reflecting the lower local symmetry, such as the mixing of the Raman and IR active modes and non-cubic crystal-field effects. Many high-symmetry solids are of this type as we will see later. 

The growth on foreign substrates typically leads to the presence of built-in strain in heteroepitaxial GaN layers owing to the difference in lattice parameters and thermal expansion coefficients between layers and substrates [19, 25-27]. Sapphire and SiC are among the most often used substrates, and typically growth is realized on the basal (0001) c-plane of sapphire and SiC. In such instances, nitride films grow along the polar [0001] direction. The sixfold symmetry of the basal planes of the wurtzite (nitrides, SiC) and rhombohedral (sapphire) crystal structures dictates their isotropy in the basal plane and hence, the thermal expansion coefficients, piezoelectric and elastic properties... 

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