An efficient approach to estimate electronic couplings in molecular pairs using molecular orbital grids: A generalization of CubeMap

Estimating electronic couplings (V) is essential to understanding the fundamental electron-transfer process between molecular systems and, consequently, developing computationally efficient approaches for their fast, yet accurate estimation is central to (bio)chemistry and materials science. We have recently proposed a novel and ultrafast approximation, called CubeMap [R. Rubert-Albiol et al., J. Chem. Phys. 162, 064105 (2025)], to evaluate V in molecular pairs. CubeMap exploits the well-known linear relationship (V = C · S) between V and the molecular orbital overlap integral (S) via a fitting constant C. Nevertheless, the original CubeMap formulation required an initial system-specific parameterization, limiting the broad and general applicability of the method for the final users. In this work, we present a significant generalization of the CubeMap method by setting a global scaling factor using a wide and diverse library (more than 80 π-conjugated molecules and 42 000 dimers). The new protocol removes the initial molecule-specific fitting, which was a computational burden, and broadens its scope for non-specialized users in a "black-box" manner. The CubeMap approach has also been extended to deal with semi-flexible molecules with minimal user input, mitigating errors arising from peripheral and/or floppy substituents. Validation across the database shows a good agreement with reference electronic structure calculations, maintaining reasonable mean absolute errors, yet with an important speed-up of up to three orders of magnitude and agreement on the resulting statistical distributions. CubeMap therefore constitutes a reliable tool for numerous evaluations of electronic couplings between molecular units and is, therefore, of great interest for large-scale simulations of charge transport.