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andrzejek

Member

Registered: 2024-12-09

Posts: 19

Issue with High K*K Value in Orca 6.0 ESD Calculations

Hello,

I’m reaching out here because I couldn’t get a clear answer from the developer’s forum.

I’m calculating ESD-associated rates like kF, kP, kISC, and kIC using the adiabatic Hessian model, thoroughly accounting for H-T, Duschinsky rotation, and generally following the suggestions provided in Manual.

Unfortunately, the K*K value is quite large — at least 18 — which prevents the proper application of the output. So far, I’ve tried the following options:
- COORDSYS CART
- IFREQFLAG REMOVE TCUTFREQ 100
- IFREQFLAG REMOVE TCUTFREQ 200

…but without success.

For testing purposes, I set:
- IFREQFLAG REMOVE TCUTFREQ 500

…but the K*K value only dropped by 1 unit.

Initially, I thought the issue might be related to hydrogen atom transfer between two adjacent residues. However, in some cases where the hydrogen is on residue 1 in one state and on residue 2 in the other, the K*K values were small — around 2-3 at most — so that doesn’t seem to be the cause. Moreover, the structure remains nearly the same between the states, with little geometric alteration.

Despite that, using USEB FALSE did not improve the K*K value, nor did setting STEPCONSTR 27 (where 27 is the [Avogadro]-1 index of the hydrogen being swapped).

Any advice or suggestions would be greatly appreciated.

Thanks!

EXAMPLE:

------------------------------------------------------------------------------
                           ORCA EXCITED STATE DYNAMICS
------------------------------------------------------------------------------

Requested calculation:                         ...ISC
Coordinate system:                             ...Deloc. Internal (BAKER)
Lineshape function:                            ...Gaussian
Excited state PES:                             ...adiabatic hessian
Apply Duschinsky rotation:                     ...yes
Use operator derivatives:                      ...yes
Convert derivatives between states:            ...no
Use same frequencies:                          ...no
Multiroot calculation:                         ...no
Single mode calculation:                       ...no
Selected mode calculation:                     ...no

Initial state hessian:                         S1.hess
Reading initial state hessian:                 ...done
Final state hessian:                           T3.hess
Reading final state hessian:                   ...done

As a TS Hessian was given, HessFlag is now AH!
Adjusting all geometries to center of mass:     ...done
Rotating the excited state geometry:           ...done
The RMSD is:                                   0.085143

Writing FS hessian to:                         kISC_1.FS.hess
Calculating Wilson’s B Matrix:                 ...done
Converting to internal coordinates:            ...done
Calculating rotation matrix J:                 ...done
Calculating displacement vector K:             ...done
The sum of K*K is:                             12.855153
WARNING! Something might be seriously wrong here.
Please check the manual about large values of K*K.

Last edited by andrzejek (2025-03-11 09:45:07)

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 1,954

Website

Re: Issue with High K*K Value in Orca 6.0 ESD Calculations

I don't have much experience in using ESD module. I would like to suggest you to post the question on "quantum chemistry" board of my computational forum: http://bbs.keinsci.com/forum-103-1.html. A Chinese ORCA developer wzkchem frequently replies ORCA questions in this forum in detail. Signing up and posting in this forum are very easy, and using English to describe question is welcomed.