While I was working today on Computational Materials Physics Course by Stefaan Cottenier, the platform suddenly stopped working. I got the following message. Hmm. We’re having trouble finding that site. We can’t connect to the server at beta.compmatphys.org. If you entered the right address, you...

I am trying to understand the construction of Hessian matrix using numerical differentiation (NUMFREQ option in ORCA for example). I understand that Hessian is a square matrix containing second derivatives of energy with respect to 3N atomic coordinates. If I try to perform a NUMFREQ calculation ...