# Restart potential energy scan in Gaussian with additional scan points

I have finished a scan of a bond length, but I need to continue the coordinate scan adding more points to the same scan.

I thought of writing a second input file from the last geometry, relaunching the scan updating the redundant coordinates. Is there another way like something scan=(restart)?.

• +1, but good edit @Phil Hasnip ! I was confused in thinking this might be about the SCAN functional :) Mar 11, 2022 at 13:54
• What do u mean by adding more points to the same scan. Do u mean for example you did the scan and the distance became 3.2 A and you want to add more points to this distance to increase or decrease the distance ? Mar 11, 2022 at 14:19
• @Abd-ElazeemMohamed I started a potential energy scan along a bend length. I set up 37 steps of 0.1 Amstrong. I calculated wrong the final distance and I'll need 47 steps. Is there a way to restart the calculation without losing the already 16 steps taken? Mar 11, 2022 at 15:16
• Can you just start the new scan where the last one finished? Mar 11, 2022 at 15:16
• @PhilHasnip ok, but is there a more efficient way? Mar 11, 2022 at 15:21

If I'm understanding correctly, something like this should work.

%oldchk=short_scan.chk
%chk=new_scan.chk
#p opt=modredundant Geom=(Checkpoint,ModRedundant)

0 1 !Or your particular charge/multiplicity

!Your new scan coordinate



This should read the last scan step from the prior checkpoint file and then you can start a new scan (or other modredundant coordinate modification) from there. This assumes you are doing a relaxed scan and not using the scan keyword to do a rigid scan. I don't know how rigid scans interact with the checkpoint file.

• Exactly what I was searching Mar 11, 2022 at 16:04