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I n layered structures the anion position has low local symmetry. The result are induced anion dipoles which strongly interact with each other and with all the remaining crystalline matrix. Two different sppronchcs are examined t o take account of the anion polarization energy in layered structures. The lattice energy is calculated with regard to the anion polarization term for some halides of bivalent metals (Mg, Ca, Cd, Mn, Pb). The polarization correction t o lattice energy is found to be large, 3 to 4 eV. Impurity dissolution energies are recalculated for those cases where the pure impurity component forms a layered structure: their values are found t o be positive and correct in order of magnitude.

The growth of series of actual laser crystals belonging to dierent structural types by the Czochralski method is presented. The primary attention is given to single crystalline compounds and their solid solutions with garnet structure (scandium-containing rare-earth garnets with general formula {LnSc}3[ScMe]2Me3O12, Me = Al, Ga) as well as with olivine (forsterite Mg2SiO4) and scheelite structure (double tungstates and molybdates with formula NaLn(TO4)2, where T = Mo or W). The broad bands of luminescence and absorption produced by activator ions in these laser hosts that appear either as a result of structural disorder (garnets, scheelites) or due to the doping by transition metal ions (chromium in forsterite) join together these representatives of dierent structural classes and determine their application in photonics. The paper considers the problems of growing of large crystals with uniform distribution of components and dopants, determination of congruently melting composition, especially in compounds with complex isomorphism. The mutual inuence of components and dopants, redistribution of ions along crystallographically non-equivalent sites in the structure, alteration of valency of transition metal ions accompanied with the change of their segregation coecients under variation of redox conditions is discussed.

Strontianite (SrCO 3 )-aragonite (CaCO 3 ) solid solutions have been simulated by the interatomic potential method. The composition dependences of the unit cell parameters, the unit cell volume, and bulk modulus have been constructed. It has been shown that the volume of the unit cell and bulk modulus show small negative deviations from additivity. The local structure of solid solutions has been analyzed. It has been established that the enthalpy of mixing is positive and, for the equimolar composition, reaches a maximum of 2.45 kJ/mol. Based on the composition dependences of the Gibbs free energy for the temperature range of 300-650 K, the solvus of the system has been constructed. According to the obtained data, the solubility of aragonite in strontianite under ambient conditions is 5.5 mol %, while that of strontianite in aragonite is 2.8 mol %. The miscibility gap of the system disappears at around 450 K. The calculated results have been com pared with the experimental data.

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