By André Julg (auth.)
Traditionally, whilst one bargains with crystals, the 1st estate to be offered is the periodicity of the lattice, and all equipment of research are in line with this attribute, that's thought of crucial. in truth, crystals fluctuate from the molecules of finite dimension which are studied in chemistry, in simple terms of their tremendous huge variety of debris. in addition, the lifestyles of faces, which restrict the unfold of crystals in area, inevitably breaks the periodicity of the approach. For those purposes it really is average to use to crystals the recommendations and techniques which have been extensively confirmed within the examine of molecules. Pauling first emphasised this aspect 1 and used it to provide an explanation for the digital constitution of crystals, regarded as countless and ideal. the purpose of this paintings is to teach, with assistance from a couple of examples, the chances provided through quantum chemistry for tackling the issues of crystal digital constitution, of crystallographic preparations in addition to their macroscopic form, and of distortion results brought on by the presence of faces. the world regarding the lifestyles of power bands (allowed or forbidden), hole, electrical, magnetic or optical houses are not touched upon.