First‑Principles Study of Vanadium Adsorption on Cu(111) and Graphene‑Covered Cu(111): Electronic, Magnetic, and Structural Insights

Abstract

We employ spin‑polarized density functional theory to investigate vanadium (V) adsorption on both pristine Cu(111) and graphene‑covered Cu(111) (Gra/Cu(111)). Two coverages—0.11 ML (1/9 ML) and 1 ML—are examined. On clean Cu(111), V prefers an interstitial site beneath the surface for both coverages, yielding adsorption energies of 2.17 eV/atom (1/9 ML) and 1.61 eV/atom (1 ML). Spin polarization is significant at low coverage (1.34 µB /atom) but vanishes at full monolayer. Introducing graphene as a buffer layer weakens the V–Cu interaction and restores a weak V–C coupling; the graphene Dirac point is largely disrupted at both coverages, while a net magnetic moment of 0.16 µB /atom emerges on the carbon lattice at 1/9 ML. These findings provide a foundation for tailoring vanadium‑based catalysts and spintronic devices on copper substrates.

Background

Heterogeneous catalysis hinges on the precise electronic and structural tuning of metal–support interfaces. Vanadium, with versatile oxidation states (+2 to +5), is a cornerstone in catalysis, battery chemistries, and nanomaterials. Yet, its interaction with the most widely studied Cu(111) surface remains underexplored, especially for early 3d transition metals. Recent advances in graphene growth on Cu(111) have opened avenues to engineer interfacial properties by inserting a two‑dimensional buffer layer.

Methods

All calculations were performed with VASP, employing the PBE functional with D2 van der Waals corrections and a 500 eV plane‑wave cutoff. A seven‑layer Cu slab with 20 Å vacuum was used; the bottom three layers were fixed. Supercells of 3×3 and 1×1 captured 1/9 ML and 1 ML coverages, respectively. Brillouin‑zone sampling utilized 8×8×1 (3×3) and 24×24×1 (1×1) k‑point meshes. Spin‑polarized total energies, charge densities, band structures, and projected densities of states (PDOS) were analyzed. Phonon dispersions were computed to confirm dynamical stability.

Results and Discussion

Vanadium on Clean Cu(111)

Seven adsorption sites were evaluated; the sub‑surface (subT) site consistently exhibited the lowest energy, with V atoms inserting beneath the top Cu layer. At 1/9 ML, V–Cu bond lengths of 2.27 Å and adsorption energy of 2.17 eV/atom were found, while at 1 ML the bond length expanded to 2.37 Å and the adsorption energy decreased to 1.61 eV/atom—indicating stronger V–V repulsion at higher coverage. Spin‑polarized calculations revealed a magnetic moment of 1.34 µB /atom at 1/9 ML, but no net magnetism at 1 ML. Band‑structure analysis shows pronounced hybridization of V d‑states with Cu d‑states near the Fermi level, driving the observed magnetism.

Graphene on Cu(111)

Graphene prefers a top‑fcc configuration on Cu(111), with a binding energy of 47 meV /atom and a separation of 3.14 Å, confirming weak physisorption. The Dirac cone is preserved but slightly down‑shifted, reflecting n‑type doping from Cu. Charge‑density deformation maps confirm electron transfer from Cu to graphene, reducing the Cu work function from 4.78 eV to 4.68 eV.

Vanadium on Gra/Cu(111)

Four sites (topA, bridge, topB, hollow) were examined. At 1/9 ML, the hollow site is most favorable (1.91 eV/atom), whereas at 1 ML the topA site dominates (1.16 eV/atom). Spin‑polarization energy rises to 390 meV/atom at 1/9 ML, yielding a V magnetic moment of 2.93 µB /atom—nearly the free‑atom value—while no magnetism appears at 1 ML. The V–C interaction is predominantly ionic at low coverage but becomes more covalent as coverage increases, as shown by deformation‑charge maps. The graphene Dirac point is destroyed in both cases, yet a small magnetic moment develops on the carbon lattice at low coverage.

Phonon Stability

Calculated phonon spectra for both V/Cu(111) and V/Gra/Cu(111) show no imaginary frequencies, confirming dynamical stability of all studied configurations.

Conclusions

First‑principles calculations reveal that V atoms favor subsurface adsorption on Cu(111), leading to strong V–Cu hybridization and coverage‑dependent magnetism. Graphene insertion mitigates V–Cu coupling, preserves weak V–C interactions, and introduces a small magnetic moment on carbon. These insights enable rational design of vanadium‑based catalysts and spintronic platforms on copper substrates.

Abbreviations

• Cu(111): (111) surface of copper
• FM: Ferromagnetic
• GGA: Generalized Gradient Approximation
• ML: Monolayer
• PAW: Projector Augmented Wave
• PBE: Perdew–Burke–Ernzerhof
• V/Cu(111): Vanadium adsorbed on Cu(111)
• V/Gra/Cu(111): Vanadium adsorbed on graphene‑covered Cu(111)
• VASP: Vienna Ab initio Simulation Package
• vdW: van der Waals