EPR-Guided Assignment of NO2 and CO2 Adsorption Motifs on MgO(100) from Embedded-Cluster DFT

TİRYAKİ Ö., UCUN F.

Applied Magnetic Resonance, vol.57, no.6-7, 2026 (SCI-Expanded, Scopus)

  • Publication Type: Article / Article
  • Volume: 57 Issue: 6-7
  • Publication Date: 2026
  • Doi Number: 10.1007/s00723-026-01842-y
  • Journal Name: Applied Magnetic Resonance
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Aerospace Database, Compendex, INSPEC, Materials Science & Engineering Collection (ProQuest), Technology Collection (ProQuest)
  • Süleyman Demirel University Affiliated: Yes

Abstract

Electron paramagnetic resonance (EPR) remains one of the most direct probes for assigning adsorbate-derived radical states on ionic-oxide surfaces, yet the connection between measured magnetic parameters and local adsorption motifs on MgO(100) is often not unique. In this work, we use an embedded-cluster density functional framework to assess NO2- and CO2-derived paramagnetic motifs on MgO(100) by directly comparing calculated g tensors, hyperfine tensors, and powder-spectrum simulations with benchmark experimental spectra. For NO2, a weakly bound terrace O2- motif reproduces the experimental EPR response most closely, whereas vacancy-bound structures show stronger binding but substantial spin redistribution and a clearly less consistent magnetic signature. For CO2, electron transfer at regular O2- sites does not by itself guarantee an EPR-active CO2- state; instead, these motifs commonly relax toward carbonate-like species with strongly reduced 13C hyperfine couplings. In contrast, hydroxylated low-coordinated environments preserve stronger adsorbate-centered spin density, and the experimental CO2- signature is most consistently represented by a family of related OH-stabilized low-coordinated motifs, especially edge and corner environments. The results provide a unified EPR-based comparison of competing NO2 and CO2- adsorption motifs on MgO(100) and identify the local environments that are most consistent with the available benchmark spectra.