Dataset for: Understanding methane cleavage on medium-entropy oxides

This dataset accompanies the article "Understanding methane cleavage on medium-entropy oxides" by S. Yuan, H. Song, Z. Wu and D. E. Jiang*. It provides site-resolved, DFT-computed adsorption energies and climbing-image nudged-elastic-band (CI-NEB) activation barriers for the first C-H bond cleavage of methane (CH4 -> CH3 + H) on the (100) surface of a medium-entropy oxide, the equimolar quaternary oxide Mg0.25Zn0.25Ni0.25Cu0.25O. It also includes the curated feature table used to learn the compact analytical activation-energy descriptor reported in the article, so that the machine-learning analysis can be reproduced directly. CONTENTS (three data files) activation.csv - 77 elementary C-H cleavage reactions (30 heterolytic, 21 homolytic-trans, 26 homolytic-cis), in 9 columns: a reaction identifier, the mechanism, the site indices and identities of the CH4-, CH3- and H-hosting sites, and the CI-NEB activation energy Ea. site_adsorption_energies.csv - single-fragment adsorption energies of H, CH3 and CH4 at each of the 16 lattice sites of the MEO (100) cell (8 metal-cation sites and 8 lattice-oxygen sites, indexed 1-16). These site indices are the same indices used in the reaction identifiers, so the per-site adsorption energies can be attached to any reaction by joining on the site index. SISSO_features_12.csv - the curated, mechanism-free 12-feature table (77 rows) that is the input to the SISSO activation-energy descriptor reported in the article (Section 3.3). It contains only continuous electronic-structure and adsorption descriptors; all mechanism indicator columns and the mechanism label have been removed (the mechanism can be recovered from activation.csv via the reaction id). SITE-NAMING SCHEME Each reaction is identified by a three-number code i_j_k: i is the cation site on which CH4 is adsorbed, j is the site that hosts the CH3 fragment after cleavage, and k is the lattice-oxygen site that hosts the abstracted H atom. For heterolytic cleavage the CH3 group remains on the original cation (j = i); for the homolytic pathways j and k are both lattice-oxygen sites, and "trans"/"cis" denote their relative geometry around the cation. COLUMN DEFINITIONS - activation.csv reaction_id: reaction identifier i_j_k. mechanism: heterolytic, homolytic_trans or homolytic_cis. ch4_cation_idx / ch4_cation: index and element of the cation i on which CH4 adsorbs. ch3_site_idx / ch3_site: index and identity of the site j hosting CH3. h_site_idx / h_site: index and identity of the lattice oxygen k hosting H. Ea_eV: CI-NEB activation energy (eV). COLUMN DEFINITIONS - site_adsorption_energies.csv site_index: site index 1-16. site_kind: cation or lattice_oxygen. site_label: cation element, or O(element) for an oxygen site. E_ads_H_eV, E_ads_CH3_eV, E_ads_CH4_eV: single-fragment adsorption energy of H, CH3 and CH4 at that site (eV). COLUMN DEFINITIONS - SISSO_features_12.csv reaction_id: reaction identifier i_j_k. Ea: CI-NEB activation energy, the target (eV). Eads_CH4_i, Eads_CH3_j, Eads_H_k: single-fragment adsorption energies of CH4 at cation i, CH3 at site j, and H at oxygen k (eV). Eads_CH3_k: single-fragment adsorption energy of CH3 evaluated at the H-hosting oxygen k (eV). q_i_ini: Bader charge of the active cation i in the CH4-adsorbed initial state (e). dq_i: initial-to-final change in the Bader charge of i (e). n_d_i: d-band occupation of cation i (electrons). dn_d_i: initial-to-final change in the d-band occupation of i (electrons). q_k: Bader charge of site k with H adsorbed on top (e). dq_k: initial-to-final change in the Bader charge of k on H capture, so the initial-state charge is q_k - dq_k (e). q_j: Bader charge of site j with CH3 adsorbed on top (e). dq_j: initial-to-final change in the Bader charge of j, so the initial-state charge is q_j - dq_j (e). NUMERICAL PRECISION All numerical values in every CSV are rounded to two decimal places. Integer columns (site indices, mechanism indicators) are stored as integers, and identifier / label columns as text. SIGN CONVENTION All energies are in eV. Adsorption energies follow E_ads(X) = E(X/slab) - E(X,gas) - E(slab), so a more negative value indicates stronger binding. Activation energies are positive. Bader charges are positive on cations and negative on lattice oxygens. COMPUTATIONAL DETAILS All calculations were performed with VASP 6 using the PBE functional, PAW pseudopotentials (Ni_pv for Ni), a 450 eV plane-wave cutoff, a 3x3x1 Gamma-centred k-mesh, and force and energy convergence thresholds of 0.05 eV/A and 1e-5 eV. A Hubbard correction (DFT+U, Dudarev) of U-J = 6.2 eV was applied to the Ni 3d states, together with Grimme DFT-D3 dispersion and spin polarisation. The surface was modelled as a five-layer 4x4 Mg0.25Zn0.25Ni0.25Cu0.25O (100) slab with at least 15 A of vacuum; the top two layers were relaxed while the bottom three were fixed at the bulk geometry. The cation sublattice was generated by random redistribution of the equimolar Mg/Zn/Ni/Cu cations over 200 independent realisations, and the configuration with one of the lowest surface energies was retained as the representative model. Transition states were located with the climbing-image nudged-elastic-band method using five intermediate images. CITATION If you use this dataset, please cite the accompanying publication: Shuai Yuan, Haohong Song, Zili Wu, De-en Jiang, "Understanding methane cleavage on medium-entropy oxides", Catalysis Science & Technology, 2026. This dataset is released under the Creative Commons Attribution 4.0 International (CC-BY-4.0) license.