Frequency calculation using Zeroed out hessian technique

Questions
#1

Hi all,
I want to remove imaginary frequency in my dimer case, where one molecular is frozen. So, I used this input to run for frequency calculation but I am facing the issue:

$molecule
0 3
Dimer coordinates
$end

$rem
BASIS = cc-pVDZ
EXCHANGE = omegaB97XD
JOB_TYPE = frequency
SCF_CONVERGENCE = 10
MAX_SCF_CYCLES = 400
MAX_CIS_CYCLES = 400
UNRESTRICTED = true
SPIN_FLIP = 1
CIS_N_ROOTS = 4
THRESH = 14
CIS_STATE_DERIVATIVE = 1
FRZN_OPT = 1
FRZ_ATOMS = 36
point_group_symmetry = false
integral_symmetry = false
SOLVENT_METHOD = PCM
$end

$solvent
DIELECTRIC 32.613000
OPTICALDIELECTRIC 1.765709
$end

$frozen_opt
37:72
$end

output:

!!!!
!!Warning*!!
!!Desired analytical derivatives not available!!
!!Finite difference job might take a long time!!
!!!!
!!********************************************!!

2-order derivative to be evaluated numerically with 1-order analytical derivatives

Checking the input file for inconsistencies… …done.

Can anyone please tell me? where I am making a mistake?

#2

What version of Q-Chem? Analytic frequencies for TDDFT with meta-GGA functionals were added in v. 5.3 so anything older than that will use finite-difference.

#3

I am using 6.1 version

#4

Spin-flip methods do not have analytic frequencies.

In general, when you encounter a problem it’s a good idea to systematically test which of the REM variables is causing the issue.