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Arivu

Member

Registered: 2025-12-27

Posts: 9

Reorganization energy and Huang-Rhys factor from ORCA 6.1.1 ESD module

I am trying to reproduce reported reorganization energies and Huang–Rhys (H–R) factors for MR-TADF materials using the ESD module in ORCA (v6.1.1). However, I am running into significant discrepancies when comparing my results with values reported in the literature, where Gaussian + MOMAP were used.

Specifically, for S₁–S₀ / S₀–S₁ transitions, the reorganization energies and H–R factors obtained from ORCA-ESD are not even qualitatively close to those reported using Gaussian/MOMAP, despite carefully following the ORCA 6.1.1 manual and recommended workflows.

One point that caught my attention is that, according to the MOMAP manual, when ORCA is used as the electronic structure backend, a NACME (nonadiabatic coupling matrix element) calculation at the ground-state geometry is required. In contrast, the ORCA ESD module does not appear to require or use NACMEs in an explicit way for evaluating reorganization energies and H–R factors.

This raises a few questions that I would appreciate input on from the community:

Are the reorganization energies and H–R factors from ORCA-ESD conceptually equivalent to those obtained via Gaussian + MOMAP, or are there known methodological differences that make direct comparison problematic?

Is the absence of explicit NACME calculations in the ORCA-ESD workflow a likely reason for the discrepancy?

Has anyone benchmarked ORCA-ESD results against Gaussian/MOMAP for TADF or MR-TADF systems?

In your opinion, are ESD-derived H–R factors and reorganization energies sufficiently reliable for publication, and under what caveats or validation steps?

Any insights, references, or personal experiences would be greatly appreciated.

sobereva

Tian Lu (Multiwfn developer)

From: Athens, Greece

Registered: 2017-09-11

Posts: 2,194

Website

Re: Reorganization energy and Huang-Rhys factor from ORCA 6.1.1 ESD module

In principle, evaluation of reorganization energies and H–R factors do not need NACME.
NACME is used by ORCA_ESD when evaluating internal conversion rate.