TURBOMOLE Users Forum

TURBOMOLE Modules => Aoforce and Numforce => Topic started by: basklau on November 03, 2009, 10:26:57 AM

Title: Unit of displacements in TURBOMOLE
Post by: basklau on November 03, 2009, 10:26:57 AM

Hi!

I'm wondering what the units of the cartesian displacements in an aoforce calcuation are? a_0, Angstrom oder something completely different?

basklau

Title: Re: Unit of displacements in TURBOMOLE
Post by: uwe on November 03, 2009, 11:55:41 AM

Hello,

aoforce does the 2nd derivatives analytically, what cartesian displacements do you refer to?

Uwe

Title: Re: Unit of displacements in TURBOMOLE
Post by: basklau on November 03, 2009, 12:56:40 PM

The output displacements (normal modes) !

basklau

Title: Re: Unit of displacements in TURBOMOLE
Post by: uwe on November 03, 2009, 02:33:29 PM

Hi,

the $vibrational normal modes are the eigenvectors of the Hessian matrix that give the direction of the modes. The vectors are for displacement in the limit -> 0 so to say.

To get coordinates that are moved along a mode, use the script screwer.

Regards,

Uwe

Title: Re: Unit of displacements in TURBOMOLE
Post by: basklau on November 03, 2009, 03:15:39 PM

Thank you! That helps!

What are the cartesian gradients printed out by screwer?


basklau

Title: Re: Unit of displacements in TURBOMOLE
Post by: uwe on November 03, 2009, 03:42:44 PM

Hi,

those from the gradient file - current coordinates, newest gradients from the last gradient calculation or geometry optimization, and the vibrational normal modes are read in to generate the new shifted coordinates.

Uwe

Title: Re: Unit of displacements in TURBOMOLE
Post by: basklau on November 09, 2009, 10:57:20 AM

What exactly is this program vibrations doing? 

Greeting basklau

Title: Re: Unit of displacements in TURBOMOLE
Post by: uwe on November 09, 2009, 05:47:59 PM

Hi,

it reads in the vibrational normal modes and moves the coordinates along the mode that one can choose. The new coordinates can then for example be used to start a new optimization - useful if you want to get rid of an imaginary frequency.

Regards,

Uwe