From iris@indigo1.kist.re.kr  Wed Nov 13 01:37:20 1996
Received: from indigo1.kist.re.kr  for iris@indigo1.kist.re.kr
	by www.ccl.net (8.8.2/950822.1) id AAA01504; Wed, 13 Nov 1996 00:42:58 -0500 (EST)
Received: by indigo1.kist.re.kr (940816.SGI.8.6.9/940406.SGI)
	for chemistry@www.ccl.net id OAA02912; Wed, 13 Nov 1996 14:43:47 -0800
Date: Wed, 13 Nov 1996 14:43:47 -0800
From: iris@indigo1.kist.re.kr (Taesung Moon)
Message-Id: <199611132243.OAA02912@indigo1.kist.re.kr>
To: chemistry@www.ccl.net
Subject: Determinant of Hessian matrix


Dear netters,

I have tried to evaluate the determinant of Hessian matrix evaluated 
using Discover3.0. The Hessian is positive definite at minimun 
conformation but some determinants are negative in my cases. 
I carried out full minimization using Quasi-Newton 
or Newton-Raphson method until maximum derivative is less than 0.00001.

For example,
---------------------------------------------------------
                      the determinant of Hessian matrix
                      ----------------------------------
 method               butane           alanine dipeptide
---------------------------------------------------------
Quasi-Newton          negative            positive
Newton-Raphson        positive            negative
---------------------------------------------------------

Please let me know the reason. 

Thanks.

-------------------------
moon@kistmail.kist.re.kr.