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`relax` drives and controls a non-linear optimization procedure to
locate the minimum (or a stationary point) of a function . In
`TURBOMOLE` is always the electronic energy, and the coordinates
will be referred to as *general coordinates*. They include
- cartesian atomic coordinates
- internal atomic coordinates
- exponents, contraction coefficients and scaling factors of basis
functions
- a global scaling factor (a common scaling factor for all basis
set exponents)

The optimization employs an iterative procedure based on gradients
of the current and, if available, previous iterations.
Various procedures can be applied: steepest descent, Pulay's
DIIS, quasi-Newton, conjugate
gradients, as well as combinations of them.
`relax` carries out:
- update of general coordinates
- update of approximate hessians if needed
- conversion of coordinates (internal
cartesian)

The mode of operation is chosen by the keywords `$optimize` and
`$interconversion` and the corresponding options, which will
be described in the following sections.

TURBOMOLE