CCL: C2v pointgroup & coordinate system / unique choices of axis

    Dear Peter:
    The notation now accepted in group theory, known as Mulliken nomenclature, was published in J. Chem. Phys., 23 (11)  1955  1997-2011. In this report you can see that, for a C2v molecule (page 2002), z-axis is the axis of symmetry, and, in the case of water, x-axis is perpendicular to the molecular plane. Thus, the molecular plane is the yz.

Dr. Francisco Partal Ureña
University of Jaén
Department of Physical and Analytical Chemistry
Campus Las Lagunillas
E-23071 Jaén        SPAIN
Phone: +34-953-21 25 55
Fax: +34-953-21 29 40

Peter Burger chburger : wrote:
Sent to CCL by: "Peter  Burger" [chburger*]
 Dear CCLers,
 the following has puzzled me for a while...
 In the C2v point group different choices have been made in the
 literature with regard to the x and y axis.
 Several books on symmetry and point groups provide
 different answers... and sometimes even choose use
 them either way in different chapters.
 For water for instance, most of them opt for the xz plane
 as the molecular plane with y pependicular to it while others
 refer to the yz as molecular plane with x perpendicular to it.
 This obviously leads to a change of the b1 and b2 symbols
 and makes comparisons somehow complicated...
 So I guess my question is - use Al Cottons or Tinkhams
 book as authorities? Is there somewhere the _real_ truth?
 PeterE-mail to subscribers: CHEMISTRY(a) or
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