Quasi-cubic approximation

The plus (minus) sign corresponds to E°7+(E°7.) E°9, E°7+ and E°7. correspond to the upper valence band states with T9, T7 and r7 symmetries, respectively. They are called A, B and C bands in that order, conventionally. The three quantities Ai, A2 and A3 can be derived from a theoretical procedure. At is directly estimated from the calculation without the spin-orbit interaction, and A2 and A3 are obtained by fitting the fully relativistically calculated top three energy levels at the T point to the above equations with the help of the obtained value of Ai. If we assume the quasi-cubic approximation (A = Ai, Ao = 3A2 = 3A3) [1,2], the energy splittings E°9 - E°7 can be rewritten as... 

TABLE 1 Spin-orbit and crystal-field splitting energies (meV) of GaN and AIN. In the quasi-cubic approximation (QCA), Aso = 3A2 = 3A3. The calculated A2 and A3 without the QCA are also listed. 

At is in units of e2/2 = Ryd.ao with ao being the Bohr radius. The results with the quasi-cubic approximation (QCA) are also listed in parentheses. 

QB QCA QCSE QE QMS QW quantum barrier quasi-cubic approximation quantum-confined Stark effect quantum efficiency quadrupole mass spectrometry quantum well... 

The quasi-cubic model approximation can be invoked to calculate the crystal-field splitting (ACf) and spin-orbit coupling (Aso) parameters from Eq [76, 159,160]... 

Organic solids have received much attention in the last 10 to 15 years especially because of possible technological applications. Typically important aspects of these solids are superconductivity (of quasi one-dimensional materials), photoconducting properties in relation to commercial photocopying processes and photochemical transformations in the solid state. In organic solids formed by nonpolar molecules, cohesion in the solid state is mainly due to van der Waals forces. Because of the relatively weak nature of the cohesive forces, organic crystals as a class are soft and low melting. Nonpolar aliphatic hydrocarbons tend to crystallize in approximately close-packed structures because of the nondirectional character of van der Waals forces. Methane above 22 K, for example, crystallizes in a cubic close-packed structure where the molecules exhibit considerable rotation. The intermolecular C—C distance is 4.1 A, similar to the van der Waals bonds present in krypton (3.82 A) and xenon (4.0 A). Such close-packed structures are not found in molecular crystals of polar molecules. 

Just as for cubic phases, the rod description of the R phase is an approximation to a hyperbolic surface. The smooth surface that defines the hydrophobic-polar interfaces resembles mesh surfaces containing a hexagonal array of pores. The genesis of this phase can also be understood as a resolution of the requirement for quasi-homogeneous interface. 

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