I’ve looked all through the Q-Chem manual (6.1) and can find no actual documentation for the NO_REORIENT logical variable. There are lots of examples, but no description of what this parameter does and how it works.
Is there another source for this information?
It forces Q-Chem to use the coordinate system in the $molecule section, as given. (By default, Q-Chem rotates the molecule into the so-called Standard Nuclear Orientation, defined by the principle axes of nuclear charge, which is nice for reproducibility purposes since quadrature grids aren’t strictly rotationally invariant, but sometimes you want to turn it off, for which you set NO_REORIENT=TRUE.)
I will add something to the manual.
Thanks. So this takes place of the
combination used in the past.
No, NO_REORIENT is unconnected to symmetry. (Those symmetry keywords did change in 6.1 and that is documented in a section called “Symmetry”.) NO_REORIENT simply controls whether Q-Chem rotates into the SNO, which is intended to normalize across different GUIs that might produce different orientations. This is what I added to the manual (which won’t roll out until 6.1.1):