IRC calculation

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Introduction to IRC calculations

IRC is short for "intrinsic reaction coordinate". It means the lowest energy path from an energy minimum over a transition state and to a minimum on the other side. An IRC calculation starts by reading the TS geometry and the corresponding force constants and thereafter it evolves towards the reactant and the product minimum.

An input example

%mem=720MB
%chk=irc.chk
#p irc=rcfc b3lyp/genecp

irc calculation from TS

0 1
76             0        1.189379   -0.031385    0.000003
 6             0        1.854439    1.797331   -0.000292
 6             0       -0.778197    0.811276   -0.000132
 6             0        0.791541   -0.757968   -1.757567
 8             0        2.253960    2.882867   -0.000469
 8             0       -1.277919    1.911456   -0.000309
 8             0        0.506620   -1.187037   -2.799938
 6             0        0.791515   -0.757439    1.757786
 6             0        2.963108   -0.839116    0.000146
 8             0        0.506576   -1.186196    2.800281
 8             0        4.013448   -1.318569    0.000243
 1             0       -3.231508    1.556656   -1.198931
 6             0       -3.608152    0.537685   -1.243217
 7             0       -3.208759   -0.166381    0.000029
 1             0       -4.701546    0.521637   -1.320457
 1             0       -3.164626    0.010722   -2.088898
 6             0       -3.608148    0.538071    1.243057
 6             0       -3.626594   -1.585341    0.000248
 8             0       -1.574263   -0.352957    0.000057
 1             0       -4.701542    0.522049    1.320306
 1             0       -3.231502    1.557027    1.198453
 1             0       -3.164619    0.011371    2.088900
 1             0       -4.720931   -1.636306    0.000234
 1             0       -3.222209   -2.066885    0.890557
 1             0       -3.222172   -2.067168   -0.889890

@/home/tfjermestad/basisSet/basisSet.txt/N