Subject: Re: CCL:complex NCA

From: "Robert Fraczkiewicz" <[email-masked]>
Date: Tue, 4 Nov 1997 11:32:11 -0600

Dear K. Hassler,

You can generate quite equivalent purely real and purely imaginary
representations by rotating in the complex plane.
An example will explain that. The E symmetry block in C3 has two types of
characters:

         1   e   e*
         1   e*  e

where e=exp(2pi/3) and p="pi"=3.14159...
By adding and subtracting these two rows you will generate real characters:

         2   2c  2c

where c=cos(2p/3) and imaginary ones:

         0  2is 2is

where s=sin(2p/3). After generating symmetry coordinates you have to normalize
them anyway, so you can kick out common factors (2 and 2i):

         1   c   c
         0   s   s

You will obtain perfectly real symmetry coordinates forming two separate E
symmetry blocks. Since they are degenerate and give the same frequencies,
you can get rid of one of them. Program RAMVIB will let you shuffle and
combine symmetry blocks and isotopomers in any fashion and order. It is
available from CCL archives:
ftp://www.ccl.net/pub/chemistry/software/SGI/ramvib/

Happy normal-coordinate-analyzing!

Robert Fraczkiewicz
University of Texas Medical Branch
Galveston, TX 77555, USA