Geometry optimization

[tigeryzz]

hi, i used Quasi Newton method to optimize a supercll with vacuum. however, it can not converge by using the default parameters, the error is "Quasi Newton minimization unable to reach minimum with given force tolerance". note that the max_steps have not reached. which parameters shoul i adjust? may i decrease the trust radius?

[Nordland]

Perhaps this could be a solution. However if we could see the convergence of the forces, I could properly guide you even more.

[tigeryzz]

Thanks~ the convergence detail are shown as follow:
# Geometry optimization step : 0
# Total Energy           =-16526.6212 eV
# Max Force Component    =     0.1047 eV/Ang
# Geometry optimization step : 1
# Total Energy           =-16526.6156 eV
# Max Force Component    =     0.0694 eV/Ang
# Geometry optimization step : 2
# Total Energy           =-16526.6072 eV
# Max Force Component    =    -0.3297 eV/Ang
# Geometry optimization step : 3
# Total Energy           =-16526.6231 eV
# Max Force Component    =     0.0708 eV/Ang
# Geometry optimization step : 4
# Total Energy           =-16526.5824 eV
# Max Force Component    =     0.7817 eV/Ang
# Geometry optimization step : 5
# Total Energy           =-16526.6247 eV
# Max Force Component    =     0.1687 eV/Ang
# Geometry optimization step : 6
# Total Energy           =-16526.4808 eV
# Max Force Component    =     1.6284 eV/Ang
# Geometry optimization step : 7
# Total Energy           =-16526.6205 eV
# Max Force Component    =     0.2656 eV/Ang
# Geometry optimization step : 8
# Total Energy           =-16526.5417 eV
# Max Force Component    =     1.4789 eV/Ang
# Geometry optimization step : 9
# Total Energy           =-16526.6236 eV
# Max Force Component    =    -0.1411 eV/Ang
# Geometry optimization step : 10
# Total Energy           =-16526.6103 eV
# Max Force Component    =     0.3657 eV/Ang
# Geometry optimization step : 11
# Total Energy           =-16526.6185 eV
# Max Force Component    =     0.2631 eV/Ang
# Geometry optimization step : 12
# Total Energy           =-16526.6095 eV
# Max Force Component    =     0.4792 eV/Ang
# Geometry optimization step : 13
# Total Energy           =-16526.5269 eV
# Max Force Component    =     1.0968 eV/Ang
# Geometry optimization step : 14
# Total Energy           =-16526.5349 eV
# Max Force Component    =     1.3849 eV/Ang
# Geometry optimization step : 15
# Total Energy           =-16526.6078 eV
# Max Force Component    =    -0.5014 eV/Ang
# Geometry optimization step : 16
# Total Energy           =-16526.6169 eV
# Max Force Component    =    -0.5166 eV/Ang
# Geometry optimization step : 17
# Total Energy           =-16526.6178 eV
# Max Force Component    =    -0.2461 eV/Ang
# Geometry optimization step : 18
# Total Energy           =-16526.6234 eV
# Max Force Component    =    -0.2057 eV/Ang
# Geometry optimization step : 19
# Total Energy           =-16526.6198 eV
# Max Force Component    =    -0.0938 eV/Ang
# Geometry optimization step : 20
# Total Energy           =-16526.6136 eV
# Max Force Component    =    -0.5022 eV/Ang
# Geometry optimization step : 21
# Total Energy           =-16526.6240 eV
# Max Force Component    =     0.1509 eV/Ang
# Geometry optimization step : 22
# Total Energy           =-16526.6170 eV
# Max Force Component    =     0.3061 eV/Ang
# Geometry optimization step : 23
# Total Energy           =-16526.6237 eV
# Geometry optimization step : 24
# Total Energy           =-16526.6234 eV
# Max Force Component    =     0.1069 eV/Ang
# Geometry optimization step : 25
# Total Energy           =-16526.6239 eV
# Max Force Component    =    -0.0614 eV/Ang
# Geometry optimization step : 26
# Total Energy           =-16526.6218 eV
# Max Force Component    =    -0.2947 eV/Ang

[Nordland]

Based on this, there is likely two reason.

Either the forces and total energy does not match very well, you could try to increase the mesh-cutoff slightly in order to see if this helps.

Alternative I would set the thrust radius down in order to try to compensate for the energy and forces numerical mismatch.

[tigeryzz]

Thanks for your advice. I have set the cut off to 300Ry. I did not understand the mismatch you mentioned well. Did you mean that the less force should correspond a lower total energy? should i increase the energy criterion(i used 1e-4Ry yet) or increase the k-points?