%0 Journal Article %T Crystallography in Spaces E<sup>2</sup>, E<sup>3</sup>, E<sup>4</sup>, E<sup>5</sup> ...N<sup>0</sup>I Isomorphism Classes: Properties and Applications to the Study of Incommensurate Phase Structures, Molecular Symmetry Groups and Crystal Families of Space E<sup>5</sup %A R. Veysseyre %A D. Weigel %A T. Phan %A H. Veysseyre %J Advances in Pure Mathematics %P 137-149 %@ 2160-0384 %D 2015 %I Scientific Research Publishing %R 10.4236/apm.2015.54017 %X This paper mainly consists of the classification of all crystallographic point groups of n-dimensional space with n ¡Ü 6 into different isomorphism classes. An isomorphism class is defined by a type of finite mathematic group; for instance, the different types of mathematic groups have been well defined and studied by Coxeter. This classification may be used in the investigation of several domains of crystallography such as the study of the incommensurate phases, the quasi crystals ¡­ Indeed, each mathematic substitution group characterizes an isomorphism class of crystallographic point groups (spaces E2 or E3), of point groups of super crystals (spaces E4 or E5), and of molecular symmetry groups (spaces E2 or E3). This mathematic group gives interesting information about: 1) the incommensurate phase structures and their phase transitions according to the Landau¡¯s theory in their super spaces E