ATC: fix_modify AtC control thermal

# fix_modify AtC control thermal

## syntax

fix_modify AtC control thermal <control_type> <optional_args>

- control_type (string) = none | rescale | hoover | flux

fix_modify AtC control thermal rescale <frequency>

- frequency (int) = time step frequency for applying velocity rescaling

fix_modify AtC control thermal hoover

fix_modify AtC control thermal flux <boundary_integration_type(optional)> <face_set_id(optional)>

- boundary_integration_type (string) = faceset | interpolate
- face_set_id (string), optional = id of boundary face set, if not specified (or not possible when the atomic domain does not line up with mesh boundaries) defaults to an atomic-quadrature approximate evaulation, does not work with interpolate

## examples

`fix_modify AtC control thermal none`
`fix_modify AtC control thermal rescale 10`
`fix_modify AtC control thermal hoover`
`fix_modify AtC control thermal flux`
`fix_modify AtC control thermal flux faceset bndy_faces`

## description

Sets the energy exchange mechansim from the finite elements to the atoms, managed through a control algorithm. Rescale computes a scale factor for each atom to match the finite element temperature. Hoover is a Gaussian least-constraint isokinetic thermostat enforces that the nodal restricted atomic temperature matches the finite element temperature. Flux is a similar mode, but rather adds energy to the atoms based on conservation of energy. Hoover and flux allows the prescription of sources or fixed temperatures on the atoms.

## restrictions

only for be used with specific transfers : thermal (rescale, hoover, flux), two_temperature (flux)
rescale not valid with time filtering activated

## related

## default

none
rescale frequency is 1
flux boundary_integration_type is interpolate