MgO geometry output: The bulk structure (conventional cell, primitive cell)

When running CRYSTAL with the previous input for MgO you will get the following output.
 

******************************************************************************* * * * CRYSTAL03 * * Release : 1.0 * * * * * * MAIN AUTHORS * * * * V.R. SAUNDERS(1), R. DOVESI(2), C. ROETTI(2), R. ORLANDO (2,3), * * C.M. ZICOVICH-WILSON(2,4), N.M. HARRISON(1,5), K. DOLL(1,6), * * B. CIVALLERI(2), I. J. BUSH(1), Ph. D'ARCO(2,7), M. LLUNELL(2,8) * * * * * * (1) COMPUTATIONAL SCIENCE & ENGINEERING DEPARTMENT - CLRC DARESBURY (UK) * * http://www.cse.dl.ac.uk/Activity/CRYSTAL * * (2) THEORETICAL CHEMISTRY GROUP - UNIVERSITA' DI TORINO - TORINO (ITALY) * * http://www.crystal.unito.it * * (3) UNIVERSITA' DEL PIEMONTE ORIENTALE - ALESSANDRIA (ITALY) * * (4) UNIVERSIDAD AUTONOMA DEL ESTADO DE MORELOS - 'CUERNAVACA (MEXICO) * * (5) IMPERIAL COLLEGE - LONDON (UK) * * (6) TU BRAUNSCHWEIG - BRAUNSCHWEIG (GERMANY) * * (7) UNIVERSITE' PIERRE ET MARIE CURIE - PARIS (FRANCE) * * (8) UNIVERSIDAD DE BARCELONA - BARCELONA (SPAIN)' * * ******************************************************************************* EEEEEEEEEE STARTING DATE 02 09 2003 TIME 08:30:00.0 MgO bulk

The header of CRYSTAL03 reports the CRYSTAL version and the main authors of the code. 
The title section from the input file follows.
 

CRYSTAL CALCULATION   (INPUT ACCORDING TO THE INTERNATIONAL TABLES FOR X-RAY CRYSTALLOGRAPHY)   CRYSTAL FAMILY                       :  CUBIC    CRYSTAL CLASS  (GROTH - 1921)        :  CUBIC HEXAKISOCTAHEDRAL    SPACE GROUP (CENTROSYMMETRIC)        :  F M 3 M

Summary of the crystallographic information. The periodicity of the system is indicated.
 

LATTICE PARAMETERS  (ANGSTROMS AND DEGREES) - CONVENTIONAL CELL          A           B           C        ALPHA        BETA       GAMMA       4.21000     4.21000     4.21000    90.00000    90.00000    90.00000     NUMBER OF IRREDUCIBLE ATOMS IN THE CONVENTIONAL CELL:    2   INPUT COORDINATES   ATOM AT. N.              COORDINATES     1  12     0.000000000000E+00  0.000000000000E+00  0.000000000000E+00     2   8     5.000000000000E-01  5.000000000000E-01  5.000000000000E-01

The lattice parameters of the conventional cell and the atomic position of the atoms in the asymmetric unit, as given in input, are reported.
 

******************************************************************************* << INFORMATION >>: FROM NOW ON, ALL COORDINATES REFER TO THE PRIMITIVE CELL *******************************************************************************

LATTICE PARAMETERS (ANGSTROMS AND DEGREES) - PRIMITIVE CELL A B C ALPHA BETA GAMMA VOLUME 2.97692 2.97692 2.97692 60.0000 60.0000 60.0000 18.65462 COORDINATES OF THE EQUIVALENT ATOMS (FRACTIONARY UNITS) N. ATOM EQUIV AT. N. X Y Z 1 1 1 12 MG 0.00000000000E+00 0.00000000000E+00 0.00000000000E+00 2 2 1 8 O -5.00000000000E-01 -5.00000000000E-01 -5.00000000000E-01 NUMBER OF SYMMETRY OPERATORS : 48

The crystallographic or conventional cell is used as standard option in input. It may be non-primitive, which means that it may not coincide with the cell of minimum volume (primitive cell) which contains just one lattice point. Note that, for maximum calculation efficiency, CRYSTAL works on the primitive cell. Hence, the conventional cell is transformed into the primitive cell (1/4 of the conventional cell), all the following structural information are referred to the primitive cell.

The transformation matrices conventional <=> primitive cell are given in Appendix A.4 of CRYSTAL03 User's Manual.

In the output file, the lattice parameters of the primitive cell and the corresponding atomic positions (in fractionary units) are reported. In this section, all the atoms in the primitive cell are displayed and indicated as equivalent atoms. For each non-equivalent atom the corresponding block of equivalent atoms is reported. For MgO two atoms only build up the primitive cell, as they are in special positions.

In figure, the conventional cell and the primitive cell, enclosed in the conventional cell, of MgO are shown:
 

CONVENTIONAL CELL	PRIMITIVE CELL

With the following banner ends the standard CRYSTAL geometry output. After that, the output file continues with the geometry output section relative to the optional keywords.
 

*******************************************************************************   * GEOMETRY MANIPULATION - INPUT COORDINATES ARE GIVEN IN ANGSTROM    *******************************************************************************