Subject: Problems with B3LYP frequencies

From: Luis Salvatella Ibáñez <[email-masked]>
Date: Thu, 29 Jul 1999 17:31:06 +0200

Dear CCLers,

 I have found some problems with the calculation of B3LYP frequencies.
Thus, for
the optimized LiH at B3LYP/3-21G level (internuclear distance = 1.6297
Angstroms), numerical computations indicate a positive frequency of
1398.9861 cm-1. Instead, analytical calculations yield an imaginary
(negative) frequency of
-1024.1595 cm-1.
 The analytical vibrational analysis of other structures optimized at
B3LYP level by using different basis sets present very large numbers of
imaginary (negative)
frequencies.
 Can anybody explain these results?

 Thank you,
                        LUIS SALVATELLA