screwer recommend negative temperature

[xiang]

Hi, I was trying to optimize a structure with negative frequencies, so I chose to use screwer. Nevertheless, it recommends me a negative step length, I am confused about what does that mean? Along the reversed eigenvector?
" RECOMMENDED STEP SHOULD BE  <  0  !  "

By the way, I found that the screwer output gives two shifted coordinates, one is " CARTESIAN COORDINATES SHIFTED ALONG MODE   1" and the one is "SHIFTED CARTESIAN COORDINATES IN PRINCIPAL AXIS SYSTEM". It seems that the first one maintains in the same coordinate as in the coord file. Why would instead the second output saved in the control file?

Many thanks

[Arnim]

As far as I understand it, screwer tries to recommend a direction of the distortion by building a scalar product of gradient and vibrational mode. In order to get to lower energies, the distortion should follow the direction of the gradient.

However, you can change the direction by typing in a negative temperature vaule.

I guess the transformation to the principal axis system is just for convenience.

Cheers,
Arnim