Action: ANGLE

Module	colvar
Description	Usage
Calculate one or multiple angle/s.
output value	type
the ANGLE involving these atoms	scalar/vector

Input

The atoms that serve as the input for this action are specified using one or more of the keywords in the following table.

Further details and examples

Calculate one or multiple angle/s.

The following input instructs PLUMED to calculate and print the angle between the vector connecting atom 2 and atom 1 and the vector connecting atom 2 and atom 3.

Click on the labels of the actions for more information on what each action computes

a1The ANGLE action with label a1 calculates the following quantities:
 Quantity   
 Type   
 Description  
a1
scalar
the ANGLE involving these atoms: ANGLECalculate one or multiple angle/s. More details ATOMSthe list of atoms involved in this collective variable (either 3 or 4 atoms)=1,2,3
PRINTPrint quantities to a file. More details ARGthe labels of the values that you would like to print to the file=a1 FILEthe name of the file on which to output these quantities=colvar

In other words, the angle that is output by the input above is calculated as:

$$\theta=\arccos\left(\frac{ r_{21}\cdot r_{23}}{ | r_{21}| | r_{23}|}\right)$$

Here $r_{ij}$ is the vector connecting the $i$th and $j$th atoms, which by default is evaluated in a way that takes periodic boundary conditions into account. If you wish to disregard the PBC you can use the NOPBC flag.

Alternatively, we can instruct PLUMED to calculate the angle between the vectors connecting atoms 1 and atom 2 and atoms 3 and atom 4 by using the following input:

Click on the labels of the actions for more information on what each action computes

a3The ANGLE action with label a3 calculates the following quantities:
 Quantity   
 Type   
 Description  
a3
vector
the ANGLE for each set of specified atoms: ANGLECalculate one or multiple angle/s. More details ATOMS1the list of atoms involved in this collective variable (either 3 or 4 atoms)=1,2,3 ATOMS2the list of atoms involved in this collective variable (either 3 or 4 atoms)=4,5,6 ATOMS3the list of atoms involved in this collective variable (either 3 or 4 atoms)=7,8,9
PRINTPrint quantities to a file. More details ARGthe labels of the values that you would like to print to the file=a3 FILEthe name of the file on which to output these quantities=colvar

It is common to assume when using this feature that all the angles being computed are indistinguishable so it makes sense to perform the same series of operations on every element of the output vector. The input file below is more approrpriate if the angles are not indistinguishable:

Click on the labels of the actions for more information on what each action computes

a4The ANGLE action with label a4 calculates the following quantities:
 Quantity   
 Type   
 Description  
a4
scalar
the ANGLE involving these atoms: ANGLECalculate one or multiple angle/s. More details ATOMSthe list of atoms involved in this collective variable (either 3 or 4 atoms)=1,2,3
a5The ANGLE action with label a5 calculates the following quantities:
 Quantity   
 Type   
 Description  
a5
scalar
the ANGLE involving these atoms: ANGLECalculate one or multiple angle/s. More details ATOMSthe list of atoms involved in this collective variable (either 3 or 4 atoms)=4,5,6
a6The ANGLE action with label a6 calculates the following quantities:
 Quantity   
 Type   
 Description  
a6
scalar
the ANGLE involving these atoms: ANGLECalculate one or multiple angle/s. More details ATOMSthe list of atoms involved in this collective variable (either 3 or 4 atoms)=7,8,9
PRINTPrint quantities to a file. More details ARGthe labels of the values that you would like to print to the file=a4,a5,a6 FILEthe name of the file on which to output these quantities=colvar

Syntax

The following table describes the keywords and options that can be used with this action