View source for CV:OPOS

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Navigation: [[Documentation]] / [[Collective Variables]] / [[CV:OPOS]]
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{{CVS}}
===Definition===
The absolute position of the point along z-axis of re-oriented coordinate system along principal moments of the tensor inertia '''I'''.

<center><math>\xi = A_{com,z}^'</math></center>

The z-axis can be reoriented to any axis of the re-oriented coordinate system.

The relation between re-oriented (') and native coordinate system is given by the transformation matrix '''T''':

<center><math>\bold A_{com}^' = \bold T \bold A_{com}</math></center>


===Specification===
Section name: '''OPOS'''
{|
| style="width: 5em;" | '''Key''' 
| style="width: 5em;" | '''Type'''
| style="width: 5em;" | '''Default'''
| '''Description'''
|-
|<hr/> || <hr/> || <hr/> || <hr/>
|-
| '''name'''
| string
|
| unique CV name
|-
| '''group_a'''
| [[Mask format|mask]]
|
| atoms specifying the point '''A'''
|-  style="vertical-align: top;"
| '''z_direction'''
| [[Mask format|mask]]
|
| single atom specifying the end of approximate z-direction vector of the re-oriented coordinate system. The vector origin is in '''A'''<sub>com</sub>. The atom must be member of the group '''A'''.
|-
| '''direction'''
| x, y, z
|
| determine direction of z-axis in the re-oriented coordinate system
|}
''Keys in bold are mandatory.''