Fractional coordinates in output of MD run

Dear Julian,

In saving output of MD run, I save the xyz movie which is in cartesian with Angstrom unit.
I did not find a keyword to add in the line of input related to output format so that I save the fractional coordinates. So, I have written a small code to convert it. Searching in the SRC files, I found the “cart2frac.F90” routine which does the job. What keyword should I add in the line related to output of the MD input to get fractional coordinates in the movie? Thanks.

Hi Mahmoud,
The short answer is that there is no keyword to do this. All the usual standard file formats for MD trajectories work with Cartesian coordinates because this choice makes sense in terms of visualisation and analysis (since you don’t want to wrap the coordinates back into the unit cell if you are computing diffusion-related properties, for example). It’s not clear why you want fractional coordinates (since most visualisation codes won’t like this), but you’ll just need to write your own post-processing conversion code/script to do the conversion, which is straightforward.

Dear Julian,

Thank you so much for your prompt reply.
It is now clear. I use my own PP code to convert when needed.

Best regards,