Optimisation from transition state geometries
Introduction
An IRC calculation is a relatively expensive calculation in terms of cpu time. There exists a cheaper alternative:
- Make a small displacement of the TS geometry along the forward and the backward direction of the eigenmode corresponding to the imaginary frequency.
- From the two geometries created, start a geometry optimisation.
- In order not to step over small hills on the energy surface, do this optimisation with a small step length.
Input example
%mem=720MB
%chk=prodOpt_b1.chk
#p scf=(conver=10) opt=(calcfc,maxstep=5,maxcycle=70) freq=internalmodes b3lyp/genecp nosymm
optimisation from TS
0 1
76 0 -0.983269 -0.024600 0.000009
6 0 -1.635059 1.808684 -0.000683
6 0 1.002562 0.806467 -0.000303
6 0 -0.600233 -0.734234 1.770918
8 0 -2.030038 2.894422 -0.001086
8 0 1.492402 1.913347 -0.000718
8 0 -0.307490 -1.181244 2.800662
6 0 -0.600203 -0.735596 -1.770350
6 0 -2.758976 -0.827633 0.000294
8 0 -0.307441 -1.183405 -2.799741
8 0 -3.815309 -1.292251 0.000450
1 0 3.461423 1.540051 1.193881
6 0 3.832917 0.518831 1.241612
7 0 3.465095 -0.180024 0.000068
1 0 4.925251 0.506760 1.356016
1 0 3.372253 -0.002424 2.083099
6 0 3.832916 0.517887 -1.242008
6 0 3.830772 -1.601406 0.000609
8 0 1.689587 -0.353491 0.000138
1 0 4.925248 0.505724 -1.356404
1 0 3.461427 1.539150 -1.195052
1 0 3.372251 -0.004009 -2.083100
1 0 4.923748 -1.699659 0.000649
1 0 3.414653 -2.076758 -0.888911
1 0 3.414651 -2.076082 0.890495
@/home/tfjermestad/basisSet/basisSet.txt/N