Abstract
We propose crystallization theory of quasicrystalline structures which does not use concepts of multidimensional crystallography for description of quasicrystalline order. On the example of the MnSiAl octagonal quasicrystal structure it is shown that it is possible to calculate the coordinates of corresponding quasilattice (QL) by constrained minimization of Landau free energy. The change from unconstrained to constrained minimization of the free energy is justified by the peculiarities of local atomic order in the considered structure. The proposed theory brings a new physical interpretation to traditional notions of multidimensional crystallography, and can be used to explain quasicrystalline structure formation with different QL.