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.