remove \mbox{} macros which are incompatible with `make pdf`

.. math::

   W = (N + 1) k T_\mbox{target} P_\mbox{damp}^2

   W = (N + 1) k T_{target} P_{damp}^2

where :math:`N` is the number of atoms, :math:`k` is the Boltzmann constant,

and :math:`T_\mbox{target}` is the target temperature of the barostat :ref:`(Martyna) <nh-Martyna>`. 

If a thermostat is defined, :math:`T_\mbox{target}` is the target temperature 

of the thermostat. If a thermostat is not defined, :math:`T_\mbox{target}` 

and :math:`T_{target}` is the target temperature of the barostat :ref:`(Martyna) <nh-Martyna>`.

If a thermostat is defined, :math:`T_{target}` is the target temperature

of the thermostat. If a thermostat is not defined, :math:`T_{target}`

is set to the current temperature of the system when the barostat is initialized.

If this temperature is too low the simulation will quit with an error.

Note: in previous versions of LAMMPS, :math:`T_\mbox{target}` would default to 

Note: in previous versions of LAMMPS, :math:`T_{target}` would default to

a value of 1.0 for *lj* units and 300.0 otherwise if the system had a temperature

of exactly zero.

If a thermostat is not specified by this fix, :math:`T_\mbox{target}` can be 

If a thermostat is not specified by this fix, :math:`T_{target}` can be

manually specified using the *Ptemp* parameter. This may be useful if the

barostat is initialized when the current temperature does not reflect the

steady state temperature of the system. This keyword may also be useful in

atc

AtC

ATC

athermal

athomps

atm

atomeye