Volume 2 Chapter 10 Search Menu REDUCED-CELL

Function

REDUCED-CELLS is used to construct a test to match a set of unit cell parameters against the reduced unit cell parameters in the CSD.

Basic QUEST Procedure

The equivalent test construction in Basic QUEST is discussed under *nCELL.

It should be read carefully before using the Graphics QUEST3D procedure.

Graphics QUEST3D Procedure

Ex. Suppose we wish to search the database for a primitive cell referred to hexagonal axes, with a = 11.592Å c = 12.983Å.

Select REDUCED-CELLS
The SEARCH menu vanishes and is replaced by the REDUCED-CELLS sub-menu - see below.

Select the Lattice Type and Crystal System, and enter values for cell params.
(Select "DEFINE-CELL" when you have completed your test)

Select P-Primitive
Select Hexagonal / Trigonal
Under alpha beta gamma tol appear the values 90.000 90.000 120.000 0.00100
Select a
```
 Please enter value:
```
Type 11.592 <R>
Under a b appear the values
11.592 11.592
Select c
```
Please enter value:
```
Type 12.983 <R>
Under c appear the value
12.983
Select DEFINE-CELL
The SEARCH menu is restored.

The above example illustrates that only the minimum required cell parameters need be specified - those defined by the symmetry are automatically assigned. Thus, for example, for cubic systems you need only supply the value of a.

If, for example, you have specified a value and wish to change it then you should re-select the parameter, eg. a. The value vanishes and a new value can be entered.

All values are rounded to 3 decimal places. Note the default value of the tolerance is very small (0.001Å). It may often be prudent to increase this value to 0.01Å or higher.

The menu-driven construction of the reduced cells test can be tedious for an anorthic cell and in such a case the user may find it convenient to input the data using COMMAND.

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Volume 2 Chapter 10 Search Menu REFRESH .