Subject: imaginary frequencies

From: <[email-masked]>
Date: 20 Apr 94 16:14:53 EST (Wed)

Dear netters,

I have done frequency calculations along the potential energy surface
right from the reactants to the transition state. At the reactants, as
expected, I get all Positive Frequencies and at the Transition State,
as again expected, I get one and only one imaginary frequency. But,
interestingly, along the surface, with respect to the reaction coordinate
of my choice, I get a negative (imaginary) frequency and it develops
to a larger imaginary frequency (i.e. for ex. -300.00 cm-1 to 
-1800.00 cm-1).  Now the question is, any point along the surface is
a neither a maxima nor a minima with respect to the other reaction
coordinate (unlike transition state which is THE maxima along the 
reaction coordinate). So why do we observe the imaginary frequency
along the surface?  These frequencies are calculated for a 
metathetical reaction like R-H + R' ----> R + H-R' where R and R'
are alkyl substrates.  Please mail your answers to the following
address :

		[email-masked]

Thanks in advance,

V. Sridhar, Dept. of I.P.C., I.I.Sc., Bangalore - 560 012 - India.

P.S: The Program used is Gaussian92.