When performing searches about cell data, the user has the choice between 2 search masks:

1. The Quick Search mode (Fig. 1) allows the user to easily search for cell parameters (lattice constants and volume) with a global tolerance. You can choose between Angstrom, pm or nm as units of length; the tolerance may only be entered as a percent value. It is possible to perform searches on experimental, reduced, standardized or on all data sets. To enter the extended search mode, click on the “Extended Search mode” button. The wildcard “*” is allowed for unspecified parts of the cell parameters. Cell parameters have to be entered in the order a, b, c, α, β, γ and have to be separated by blanks.

2. The Extended Search mode (Fig. 2) allows a more detailed search on individual cell parameters. You can enter individual tolerances for each single lattice parameter, for which the units of lengths can be chosen as Angstrom, pm or nm. Additionally, you can choose between absolute or relative tolerances on the search terms. Clicking on the button in the top right of the search mask opens the "Quick Search mode".

Note: Switching between Extended and Quick Search mode will keep the data you entered. The other way around is a bit more complicated, because individual tolerances have to be reduced to an overall tolerance. In this case the smallest tolerance is used.

The search fields are combined by logical AND.

The Cell reduction procedure is the same for both search masks and will be discussed together.

 

Figure 1: Cell search screen (Quick Search mode)

 

Figure 2: Cell search screen (Extended Search mode)

 

Examples (Quick Search mode), Angstrom units assumed:

Cell parameters	Cell Volume	Tolerance/%	will find all entries with
3.8 3.8 3.8 90 90 90			exactly the entered data: cells with a=b=c=3.8 and all angles 90°
3.8 3.8 3.8 90 90 90	60		no results
3.8 3.8 * 90 90 90			cells with a=b=3.8 and all angles 90°; c is unspecified
* * * 90 90 90	510	5	cells with arbitrary a, b and c and all angles in the range 85.5° to 94.5° and a volume range of 484.5 to 535.5 Å3

 

Examples (Extended Search mode), Angstrom units and absolute tolerances assumed:

Cell parameters													Cell Volume		will find all entries with
a	Δa	b		Δb	c	Δc	α	Δα	β	Δβ	γ	Δγ	V	ΔV
5.1	0.2	6.7		0.7	10.8	0.9	100	5	102	3	107	0.3			a: 4.9 … 5.3; b: 6.0 … 7.4; c: 9.9 … 11.7; α: 95 … 105°; β: 99 … 105°; γ: 106.7 … 107.3°
4.9	0.1						90		97.1	0.3	90		310	10	triclinic cells or monoclinic cells with b as the unique axis; a: 4.8 … 5.0; b and c unspecified; monoclinic angle β: 96.8 … 97.4°; cell volume V: 300 … 320 Å3

 

Reduced Cell Search

You can search for reduced cell data in the following different ways:

1. Activate the checkbox “Reduce Cell data”. The dropdown box “Search cell data” will change to the “Reduced Cell” data set; additionally the box will be deactivated. Select the lattice centering. Now enter the experimental cell data. The system will reduce the entered cell and perform a search in the reduced cell dataset.

2. Select the reduced cell dataset from the dropdown box (Fig. 3). Enter the cell data in the appropriate fields (if cell reduction was performed in an earlier step). The entered data will be treated as reduced cell data.

3. Select “All cell data” for searching in experimental, standardized and reduced cell data sets.

In contrast to the “Quick search” the “Extended search” allows the user to restrict the search to one crystal system (Fig. 4).

 

Figure 3: Dataset selection

 

Figure 4: Restricting the search to a certain crystal system