CRYST1
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.
COLUMNS DATA TYPE FIELD DEFINITION
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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.
If the 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
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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.
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