# Machine-learned interatomic potentials

Excited-state energies, unlike ground-state energies, are not sums of atomic contributions, so multistate readouts that pool atomic terms drift when molecules grow larger or two molecules appear together. LEH-MACE instead assembles a symmetric matrix from one diagonal block per atom and coupling blocks for atom pairs, and takes its eigenvalues as the singlet excitation energies, so the spectrum of two molecules beyond the cutoff is exactly the union of their spectra. On TD-DFT data for about 303,000 geometries of 106,933 molecules, the advantage grew away from the training distribution, and only this construction kept single-molecule accuracy for molecule pairs.

Excited-state energies, unlike ground-state energies, are not sums of atomic contributions, so multistate readouts that pool atomic terms drift when molecules grow larger or two molecules appear together. LEH-MACE instead assembles a symmetric matrix from one diagonal block per atom and coupling blocks for atom pairs, and takes its eigenvalues as the singlet excitation energies, so the spectrum of two molecules beyond the cutoff is exactly the union of their spectra. On TD-DFT data for about 303,000 geometries of 106,933 molecules, the advantage grew away from the training distribution, and only this construction kept single-molecule accuracy for molecule pairs.

Whether hydrogen sulphide physisorbs or dissociates on nanoscale refractory oxide surfaces had been hard to settle because the configuration space is too large to enumerate. This work pairs unbiased automated adsorption sampling with an off-the-shelf atomistic foundation model: MACE's MPA screens candidate minima, each survivor is re-optimised with PBE-D2*(N) and HSE06 DFT, and DFT multiconfigurational infrared spectra are compared with in situ spectra at 150 K. The computed spectra reproduce the red-shift order of the H–S stretch across the three materials: silica at 2603 cm⁻¹, forsterite at 2588 cm⁻¹ and MgO at 2504 cm⁻¹.

Whether hydrogen sulphide physisorbs or dissociates on nanoscale refractory oxide surfaces had been hard to settle because the configuration space is too large to enumerate. This work pairs unbiased automated adsorption sampling with an off-the-shelf atomistic foundation model: MACE's MPA screens candidate minima, each survivor is re-optimised with PBE-D2*(N) and HSE06 DFT, and DFT multiconfigurational infrared spectra are compared with in situ spectra at 150 K. The computed spectra reproduce the red-shift order of the H–S stretch across the three materials: silica at 2603 cm⁻¹, forsterite at 2588 cm⁻¹ and MgO at 2504 cm⁻¹.