From Online Dictionary of Crystallography
Revision as of 06:13, 31 January 2006 by AndreAuthier
Espace direct (Fr). Direktes Raum (Ge). Espacio directo (Sp).
The direct space (or crystal space) is the point space, En, in which the structures of finite real crystals are idealized as infinite perfect three-dimensional structures. To this space one associates the vector space, Vn, of which lattice and translation vectors are elements. It is a Euclidean space where the scalar product of two vectors is defined. The two spaces are connected through the following relations:
(i) To any two points P and Q of the point space En a vector PQ = r of the vector space Vn is attached
(ii) For each point P of En and for each vector r of Vn there is exactly one point Q of En for which PQ = r holds
(iii) If R is a third point of the point space, PQ + QR = PR
Section 8.1 of International Tables of Crystallography, Volume A