53 lines
1.5 KiB
Markdown
53 lines
1.5 KiB
Markdown
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# group
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```sh
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group id selection shape ...
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```
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## Inputs
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`id` - assigned id for the group.
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`selection` - either `atoms`, `elements`, or `all`.
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`shape` - either `block`, `sphere`, or `type`.
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**Additional arguments depend on the group shape passed and are listed below:**
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```sh
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group id selection block xlo xhi ylo yhi zlo zhi
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```
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where `{x,y,z}lo` are the lower bounds along `x,y,z` and `{x,y,z}hi` are the upper bounds along `x,y,z`.
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```sh
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group id selection sphere x y z r
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```
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where `x y z` define the centroid of the sphere and `r` defines the radius of the sphere.
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```sh
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group id selection type n
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```
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where `n` is a number which selects the `n`th atom type.
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## Examples
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```sh
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group tophalf all block -inf inf -inf inf inf*0.5 inf
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group precip atoms sphere 100 78 78 10
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group Ni atoms type 2
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```
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## Description
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The group option is used in conjunction with other commands which require a group input.
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**A default `all` group is defined which contains all atoms and elements.**
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A subsection of all atoms or elements can be selected using the group command.
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`id` is used to refer to the group in other commands.
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`selection` determines which element types are selected within the group.
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A group can be defined containing only `atoms`, `elements`, or `both`.
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If element types are within the bounds of the group but are not specified with `selection` they are not defined as members of the group.
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All positions for the group command can be specified using position specifications described [here](../Misc/position.md).
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