The Crystallographic Section describes the geometry of the crystallographic experiment and the coordinate system transformations.
Overview
The CRYST1 record presents the unit cell parameters, space group, and Z value. If the structure was not determined by crystallographic means, CRYST1 simply defines a unit cube.
Record Format
COLUMNS DATA TYPE FIELD DEFINITION ------------------------------------------------------------- 1 - 6 Record name "CRYST1" 7 - 15 Real(9.3) a a (Angstroms). 16 - 24 Real(9.3) b b (Angstroms). 25 - 33 Real(9.3) c c (Angstroms). 34 - 40 Real(7.2) alpha alpha (degrees). 41 - 47 Real(7.2) beta beta (degrees). 48 - 54 Real(7.2) gamma gamma (degrees). 56 - 66 LString sGroup Space group. 67 - 70 Integer z Z value.
Details
* If the coordinate entry describes a structure determined by a technique other than crystallography, CRYST1 contains a = b = c = 1.0, alpha = beta = gamma = 90 degrees, space group = P 1, and Z = 1.
* The Hermann-Mauguin space group symbol is given without parenthesis, e.g., P 43 21 2. Please note that the screw axis is described as a two digit number.
* The full international Hermann-Mauguin symbol is used, e.g., P 1 21 1 instead of P 21.
* For a rhombohedral space group in the hexagonal setting, the lattice type symbol used is H.
* The Z value is the number of polymeric chains in a unit cell. In the case of heteropolymers, Z is the number of occurrences of the most populous chain.
As an example, given two chains A and B, each with a different sequence, and the space group P 2 that has two equipoints in the standard unit cell, the following table gives the correct Z value.
Asymmetric Unit Content Z value
-----------------------------------
A 2
AA 4
AB 2
AAB 4
AABB 4
* In the case of a polycrystalline fiber diffraction study, CRYST1 and SCALE contain the normal unit cell data.
Verification/Validation/Value Authority Control
The given space group and Z values are checked during processing for correctness and internal consistency. The calculated SCALE is compared to that supplied by the depositor. Packing is also computed, and close contacts of symmetry-related molecules are diagnosed.
Relationships to Other Record Types
The unit cell parameters are used to calculate SCALE. If the EXPDTA record is NMR, THEORETICAL MODEL, or FIBER DIFFRACTION, FIBER, the CRYST1 record is predefined as a = b = c = 1.0, alpha = beta = gamma = 90 degrees, space group = P 1 and Z = 1. In these cases, an explanatory REMARK must also appear in the entry. Some fiber diffraction structures will be done this way, while others will have a CRYST1 record containing measured values.
Example
1 2 3 4 5 6 7
1234567890123456789012345678901234567890123456789012345678901234567890
CRYST1 52.000 58.600 61.900 90.00 90.00 90.00 P 21 21 21 8
CRYST1 1.000 1.000 1.000 90.00 90.00 90.00 P 1 1
CRYST1 42.544 69.085 50.950 90.00 95.55 90.00 P 1 21 1 2
Known Problems
No standard deviations are given.