compute temp/sphere command


compute ID group-ID temp/sphere keyword value ...
  • ID, group-ID are documented in compute command

  • temp/sphere = style name of this compute command

  • zero or more keyword/value pairs may be appended

  • keyword = bias or dof

    bias value = bias-ID
      bias-ID = ID of a temperature compute that removes a velocity bias
    dof value = all or rotate
      all = compute temperature of translational and rotational degrees of freedom
      rotate = compute temperature of just rotational degrees of freedom


compute 1 all temp/sphere
compute myTemp mobile temp/sphere bias tempCOM
compute myTemp mobile temp/sphere dof rotate


Define a computation that calculates the temperature of a group of spherical particles, including a contribution from both their translational and rotational kinetic energy. This differs from the usual compute temp command, which assumes point particles with only translational kinetic energy.

Both point and finite-size particles can be included in the group. Point particles do not rotate, so they have only 3 translational degrees of freedom. For 3d spherical particles, each has 6 degrees of freedom (3 translational, 3 rotational). For 2d spherical particles, each has 3 degrees of freedom (2 translational, 1 rotational).


This choice for degrees of freedom (dof) assumes that all finite-size spherical particles in your model will freely rotate, sampling all their rotational dof. It is possible to use a combination of interaction potentials and fixes that induce no torque or otherwise constrain some of all of your particles so that this is not the case. Then there are less dof and you should use the compute_modify extra command to adjust the dof accordingly.

The translational kinetic energy is computed the same as is described by the compute temp command. The rotational kinetic energy is computed as 1/2 I w^2, where I is the moment of inertia for a sphere and w is the particle’s angular velocity.



A kinetic energy tensor, stored as a 6-element vector, is also calculated by this compute. The formula for the components of the tensor is the same as the above formulas, except that v^2 and w^2 are replaced by vx*vy and wx*wy for the xy component. The 6 components of the vector are ordered xx, yy, zz, xy, xz, yz.





For the bias keyword, bias-ID refers to the ID of a temperature compute that removes a “bias” velocity from each atom. This allows compute temp/sphere to compute its thermal temperature after the translational kinetic energy components have been altered in a prescribed way, e.g. to remove a flow velocity profile. Thermostats that use this compute will work with this bias term. See the doc pages for individual computes that calculate a temperature and the doc pages for fixes that perform thermostatting for more details.

For the dof keyword, a setting of all calculates a temperature that includes both translational and rotational degrees of freedom. A setting of rotate calculates a temperature that includes only rotational degrees of freedom.

Output info






All particles in the group must be finite-size spheres, or point particles with radius = 0.0.


The option defaults are no bias and dof = all.