Off-diagonal elements of the CI matrix

From: "Gustavo Moura" <gustavo -8 at 8- hathi.chem.pitt.edu>
Subject: Off-diagonal elements of the CI matrix
Date: Wed, 5 Aug 1998 17:19:28 -0400

 Dear CCL readers,
 	I am writing a program to do CI calculations on some conjugated
 molecules using semiempirical (PPP) parameters. Unfortunately, I am having
 problems to calculate the off-diagonal elements of the CI matrix. In their book
 Szabo e Ostlund show (tables 2.3 and 2.4) how to calculate these elements when
 the determinants are in maximum coincidence. I am looking for references where
 I
 can find the answer to the following simple(?) question:
 HOW TO CALCULATE THE NUMBER OF PERMUTATIONS NECESSARY TO OBTAIN MAXIMUM
 COINCIDENCE BETWEEN THE DETERMINANTS?
 In other words:
 WHEN SHOULD I MULTIPLY THE EQUATIONS SHOWN IN THE BOOK BY -1?
 	Thank you very much in advance. I will sumarize.
 	Sincerely yours,
 				Gustavo L.C. Moura
 			    gustavo -8 at 8- hathi.chem.pitt.edu