Small negative frequency after relaxation
Posted: Wed Nov 20, 2013 2:44 pm
Hi, I am using B3LYP for relaxation of HfO2 defect system.
In my calculation, the convergence conditions were EDIFF=1E-4;EDIFFG=-0.05. NSW was set to 60. After 60 ionic steps, EDIFFG=-0.05 was not reached. The largest force was about 0.09 eV/angstrom.
I then checked the frequencies for the system after relaxation and found 3 small negative frequencies (5.68, 7.32, 10.21 cm-1):
Other frequencies are:
the largest
...
the smallest
Are these small frequencies acceptable? How can I eliminate them?
Also, I used this structure as a reactant to do transition state search by NEB.
In the image with highest energy, there exist 4 negative frequencies: 3 small negative frequencies and 1 big negative frequency. (as below, 3.52, 4.86, 6.25, and 69.81 cm-1)
Can I accept this structure as the transition state? Is this result reliable consider the 3 negative frequencies?
<span class='smallblacktext'>[ Edited ]</span>
In my calculation, the convergence conditions were EDIFF=1E-4;EDIFFG=-0.05. NSW was set to 60. After 60 ionic steps, EDIFFG=-0.05 was not reached. The largest force was about 0.09 eV/angstrom.
I then checked the frequencies for the system after relaxation and found 3 small negative frequencies (5.68, 7.32, 10.21 cm-1):
Code: Select all
64 f/i= 0.170327 THz 1.070198 2PiTHz 5.681508 cm-1 0.704418 meV
65 f/i= 0.219475 THz 1.379001 2PiTHz 7.320892 cm-1 0.907675 meV
66 f/i= 0.306052 THz 1.922983 2PiTHz 10.208803 cm-1 1.265731 meV
the largest
Code: Select all
1 f = 24.876753 THz 156.305247 2PiTHz 829.799125 cm-1 102.882016 meV
2 f = 24.510721 THz 154.005404 2PiTHz 817.589635 cm-1 101.368232 meV
the smallest
Code: Select all
62 f = 2.231141 THz 14.018675 2PiTHz 74.422865 cm-1 9.227263 meV
63 f = 1.684326 THz 10.582932 2PiTHz 56.183062 cm-1 6.965814 meV
Also, I used this structure as a reactant to do transition state search by NEB.
In the image with highest energy, there exist 4 negative frequencies: 3 small negative frequencies and 1 big negative frequency. (as below, 3.52, 4.86, 6.25, and 69.81 cm-1)
Code: Select all
63 f/i= 0.105598 THz 0.663491 2PiTHz 3.522365 cm-1 0.436718 meV
64 f/i= 0.145844 THz 0.916366 2PiTHz 4.864840 cm-1 0.603164 meV
65 f/i= 0.187444 THz 1.177747 2PiTHz 6.252469 cm-1 0.775208 meV
66 f/i= 2.092793 THz 13.149407 2PiTHz 69.808064 cm-1 8.655100 meV
<span class='smallblacktext'>[ Edited ]</span>