Single point calculations
*************************

A single point calculation is the simplest task available in the AMS
driver. It simply runs the engine once for the given geometry. In
other words, the AMS driver does not explore the potential energy
surface (PES), but simply samples a "single point" of it.

A single point calculation is performed by selecting it with the
"Task" keyword:

   Task SinglePoint

Note that a single point calculation in AMS includes the calculation
of PES point properties. Many of these, such as the nuclear gradients
and the Hessian, are derivatives at this PES point with respect to
nuclear displacements. These derivatives might be done numerically by
the AMS driver, in which case it would technically run the engine
multiple times and sample PES points around the initial point.
However, in AMS this is still considered a single point calculation.
Take for example the calculation of the normal modes of vibration of a
molecule. This used to be a separate task in the 2017 release of the
DFTB program, but in AMS is just a single point calculation with a
request for normal modes:

   Task SinglePoint

   Properties
      NormalModes True
   End

See the manual section on PES point properties for an overview of
which properties can be calculated with the "SinglePoint" task in AMS.
