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Option: velocity


-velocity <T>


This option assigns a random velocity vector to each atom, so as to comply to a Maxwell-Boltzmann distribution of velocities, and so that the sum of velocities is zero (no global drift of the system). The target temperature <T> must be given in Kelvin.

After applying this option, the distribution of velocities is computed and written to the file velocity_dist.dat.

Note that this option attempts to generate random velocities along the cartesian X, Y and Z axis for each atom, therefore it is largely non-reproducible, i.e. starting from the exact same system and applying the present option will likely lead to different results.

By default velocities are defined in Å/ps, units can be changed thanks to the option -unit. In order to specify atom velocities manually, one can use the option -properties. To remove all velocities one can use the option -remove-property to remove the properties vx, vy and vz.

If velocities were defined previously, they are replaced by those set with this option.

If a selection was defined (with the option -select) then the distribution of velocities is applied only to selected atoms. Non-selected atoms keep their velocities if they were defined, or else are assigned a zero velocity.


By default the velocity of atoms is undefined or unchanged.


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