Author Topic: checking number of negative eigenvalues  (Read 7546 times)

gojimeo

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checking number of negative eigenvalues
« on: February 06, 2008, 10:02:43 AM »
Hi all,

I wonder if there is any way to check the number of negative eigenvalues of the (approximate) hessian matrix when performing a minimization (itrvec 0, update bfgs) using statpt. I have found that when optimizing to TS (itrvec 1, update powell) statpt automatically shows the value of the 5 first eigenvalues and therefore a warning if the hessian has wrong inertia. This is very usefull when optimizing in cartesians (sometimes I must start with redundants and then to reach the required stationary point in cartesians), because if you can realize that the hessian has wrong inertia when reaching the convergence criteria, you can try to remove the little negative frequencies (tighting the convergence criteria or something) just before performing long time-demanding frequency calculations (always with NumForce in my case).

Gonzalo Jiménez-Osés

turbomaster

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Re: checking number of negative eigenvalues
« Reply #1 on: February 17, 2008, 10:09:55 PM »
Hi,

statpt will print out a warning if there are negative Hessian eigenvalues when performing minimization. It will not print the values, though. In some spare time we wil add also printing the values, its a good idea   So, the warning is there if the Hessian has negative eigenvalues!

Best regards,

Marek

gojimeo

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Re: checking number of negative eigenvalues
« Reply #2 on: February 28, 2008, 10:21:17 PM »
Hi,

OK, Marek, that´s a very interesting observation for me (I should have realized it by myself, shouldn't I?  . Thanks you for your interest. I am really glad to contribute in some manner to the development of this nice code. Keep on working hard and the best of luck for you!

Gonzalo