The restart key
***************

The name of the restart file must be provided via the "EngineRestart"
key in the AMS driver part of the input (see below). A list of data
items is read from the file (if present in the file and only as far as
significant for the new run) and used unless their usage is explicitly
suppressed by the user.

Simple usage:

   $AMSBIN/ams << eor
     ...

     EngineRestart restartfile

     Engine ADF
       ...
     EndEngine
   eor

"restartfile"
   The name of a file with restart data. The path (absolute or
   relative) to the file must be included if the file is not local to
   the directory where the calculation executes. In most cases it will
   be an "adf.rkf" file from an ADF calculation, but this is not
   necessary. It may be any file constructed by the user, for
   instance, provided it has the right structure. It must be a KF file
   and the data to be used must be stored in sections and under
   variable names, exactly how such data are generated by a normal ADF
   run in "adf.rkf" or in the checkpoint file TAPE13. Note: the
   filename must not be one of the standard filenames used internally
   by the program, such as "adf.rkf", TAPE13, etc. Generally: don't
   use a name like TAPEnn where nn is a two-digit number.

One can also specify a list of restart options in the "ADF" part of
the input:

    Engine ADF
      ...
      ...
      Restart
        optionlist
        optionlist
        ...
      End
   EndEngine

This is the list of possible options:

"noSCF"
   Do not use any fit coefficients from the restart file as a first
   approximation to the (fitted) SCF density for the new calculation.
   Instead, the sum-of-fragments density will be used, as in a non-
   restart run. Note, typically noSCF should be used in combination
   with noORB.

"noORB"
   Do not use orbitals from the restart file.

"SPINFLIP atomnumbers"
   See the separate section about the spin-flip method for converging
   broken-symmetry systems.

Note: In ADF2020, AMS handles tasks related to exploring the PES. For
restarts related to, for example, a Linear Transit, IRC, or IR
Frequencies run, one should look in the AMS manual.
