But we have encountered a new problem. We would like to get the total energy along the IRC direction, but we cannot find the values of the intrinsic reaction coordinate. And through I-Qmol only GEOMETRY vs Energy figure can be observed. Waiting for your reply.And How is the IRC figure obtained?

As mentioned here:

the string is not a rigorous IRC. To determine the latter, use JOBTYPE=RPATH.

Thank you for your help. We calculate the transition state from reactant and product structures and added “JOBTYPE rpath”. The input file command is as follows:

$rem

JOBTYPE fsm

METHOD pbe0

DFT_D = D3_BJ

BASIS aug-cc-pVTZ

FSM_NGRAD 3

FSM_NNODE 18

FSM_MODE 2

FSM_OPT_MODE 2

SYMMETRY false

SYM_IGNORE true

$end

@@@

$molecule

read

$end

$rem

JOBTYPE ts

METHOD pbe0

DFT_D = D3_BJ

BASIS aug-cc-pVTZ

THRESH 14

SCF_ALGORITHM DIIS

SCF_CONVERGENCE 8

SCF_MAX_CYCLES 1000000000

SCF_GUESS read

GEOM_OPT_HESSIAN read

MAX_SCF_CYCLES 250000000

MAX_DIIS_CYCLES=100000000

GEOM_OPT_DMAX 50

GEOM_OPT_MAX_CYCLES 10000000

GEOM_OPT_TOL_DISPLACEMENT=60

GEOM_OPT_TOL_GRADIENT 20

GEOM_OPT_TOL_ENERGY 20

mem_total = 85000

SYMMETRY false

SYM_IGNORE true

$end

@@@

$molecule

read

$end

$rem

JOBTYPE freq

BASIS aug-cc-pVTZ

METHOD pbe0

DFT_D = D3_BJ

SCF_GUESS read

$end

@@@

$molecule

read

$end

$rem

JOBTYPE rpath

BASIS aug-cc-pVTZ

METHOD pbe0

DFT_D = D3_BJ

SCF_GUESS read

RPATH_MAX_CYCLES 250000000

$end

However, where do we look for the correct IRC figure?in .out/Vfile.txt/stringfile.txt/perp_grad_file.txt

At present, i observe the figure by IQMOL is ambiguous and not smooth.Waiting for your reply.

It’s unlikely than anyone can diagnose this problem without the full input file (including coordinates). Furthermore, it is helpful to provide a minimalist example that runs quickly (small molecule and small basis sets). Along those lines, I don’t know why anyone would optimize geometries at PBE0+D3 level using aug-cc-pVTZ basis. Shouldn’t be that sensitive to basis set, 6-31G(d) or 6-31+G(d) is probably just as good and much faster.