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Published in final edited form as: Surf Sci. 2021 Oct 6;716:121960. doi: 10.1016/j.susc.2021.121960

Atomic Structures of Single-Layer Nanoislands of Ni, Cu, Rh, Pd, Ag, Ir, Pt, Au Supported on Au(111) from Density Functional Theory Calculations

Tania C Fernández-Félix 1, Juan A Santana 1,*
PMCID: PMC8562674  NIHMSID: NIHMS1749071  PMID: 34737461

Abstract

We have used density functional theory calculations to study the atomic structure of single-layer nanoislands of metal M (M=Ni, Cu, Rh, Pd, Ag, Ir, Pt, Au) supported on M(111) and Au(111) surfaces. Nanoislands of Cu, Pd, Ag, Pt, and Au have planar structures on Au(111), while nanoislands of Ni, Rh, and Ir are nonplanar. The calculations also show that nanoislands of Cu, Pd, Pt, and Au on Au(111) with a diameter below 3 nm can have one of several atomic structures. Two of these structures have atoms at the edges of the nanoislands located near bridge sites on Au(111), and the other structures have atoms at the edges and center of the nanoislands located near bridge sites. The relative stability of these atomic structures depends on the size and nature of the Au-supported nanoparticles. Our findings provided computational support for the work of Liao and Ya [J. Phys. Chem. C. 121 (2017) 19218–19225] reporting the formation of two phases of Pt nanoislands on Au(111). These findings also reveal the rich and complex atomic structures of small single-layer metal nanoislands supported on metal surfaces.

Keywords: Mixed-metal catalysts, nanostructured surfaces, d-band center model, lateral constraints, overlayered systems

1. Introduction

Two-dimensional metal-supported metal nanoparticles (single-layer nanoislands) show catalytic properties superior to regular and overlayered surfaces [1-13]. One of the critical aspects of single-layer nanoislands is their atomic structure. The atomic structure of metal-supported single-layer nanoislands results from an interplay between the size-dependent compressive stress coming from the strain caused by finite-size effects [6,14] and the compressive or tensile strain of the substrate. Such interplay can result in intriguing surface properties. For instance, Liao and Ya [2] report the formation of Pt nanoislands with two distinctive phases. In one of the phases, labeled as the R phase by the authors, the Pt atoms were not aligned with the substrate and instead were located on fcc, hcp, and asymmetric sites on Au(111), with a Pt-Pt spacing of 272 pm [2]. In the second phase, the Pt nanoislands show a Moire pattern (M phase), with a Pt-Pt distance of 269 pm [2]. Moreover, Liao and Ya [2] also found that the R phase is a more active catalyst toward the hydrogen evolution and oxidation reactions (HER/HOR) than the M phase. Those findings are encouraging, showing that metal-supported metal nanoislands are complex interfacial systems with multiple properties that could be used to design better catalysts.

The interplay between the size-dependent compressive stress [15,16] in metal-supported metal nanoislands and the compressive or tensile strain of the substrate has been previously explored computationally [17-19] employing Monte Carlo and Molecular Dynamics in conjunction with classical and embedded atom method (EAM) potentials. For instance, Jalkanen et al. [19] studied single-layer nanoislands of Cu with 5 to 120 atoms supported on Pd(111), with the metal interactions described by EAM potentials. Jalkanen et al. [19] found that single-layer nanoislands of Cu with less than 41 atoms have atomic structures where all Cu atoms are on fcc sites on Pd(111). In contrast, single-layer nanoislands of Cu with more than 60 atoms have structures where Cu atoms are located on fcc, bridge, and hcp sites on Pd(111). These simulations with model potentials critically depend on whether the potential captures the essential physics of the system; EAM potentials have only recently [20-22] been improved to capture the low electron-density environments in nanoparticles. Instead of model potentials, Density Functional Theory (DFT) calculations are now commonly used to reveal details on the energetic, structural, and electronic properties of various model metal-supported metal nanoparticles [6,23,14,24-34]. For these metallic systems, DFT calculations are more reliable than model potentials but at a notably higher computational cost. DFT studies of metal-supported metal nanoparticles are often limited to subnanometer-size model particles [24-26,28,31-35] or models of pseudomorphic overlayers [36,37]. Recently, the application of DFT to study metal-supported metal nanoparticles with diameters of a few nanometers [6,14,23,24,27,29,30] has become possible thanks to advances in computer capability and algorithms.

In the present work, we use density functional theory (DFT) methods to study the atomic structure of single-layer nanoislands of M elements (M= Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au) supported on Au(111). Single-layer nanoislands typically consist of Pd or Pt supported on Au(111) [1-12,38-43], but other bimetallic nanoislands have also been explored, including Ni/Au [44-49], Cu/Au [50-54], Rh/Au [55-60], Pd-Rh/Au [61], Ag/Au [62,63], Ag/Au [62,63], Ir/Au [42], Au-Ag [64], Ir/Ni [42], Ag/Cu [65], Rh/Pd [66], Pd/Pt [13], Ir/Pt [42], and Pt/Cu [67]. We seek to identify atomic structures of single-layer metal nanoislands on Au(111) and provided insights into their geometric, energetic, and electronic properties.

2. Computational Methodology

Our calculations are based on DFT within the Generalized Gradient Approximation (GGA) as implemented in the Vienna Ab-initio Simulation Package (VASP) [68-70]. We used the Perdew–Burke–Ernzerhof (PBE)[71] parameterization of the exchange-correlation energy functional and the projector augmented wave (PAW) [72,73] method to represent ionic cores. We employed an energy cut-off of 280 eV for the plane-wave basis set. Calculations were carried out in spin-neutral conditions, with a level broadening of 0.05 eV. Calculations with spin-polarized and spin-neutral conditions yielded similar results; see Table S1 in the supplementary material.

Single-layer nanoislands Mn (n = 19, 37, 61, and 91) were simulated on Au(111) with hexagonal models on (6×6), (8×8), (10×10), and (12×12) surface models of four atomic layers, separated by a vacuum region of over 1 nm. The use of these hexagonal models allows to simulate nanoislands with enough separation from their translational images to reduce direct interactions [34]. Similar models were used to study nanoislands on M(111) surfaces. These models of metal-supported nanoislands capture many of the physical and chemical properties of metals supported on (111) surfaces, including the size-dependent compressive stress [15,16] in the nanoislands and the compressive or tensile strain of the substrate [27,30]. Nevertheless, the models are limited to well-defined (111) surfaces; without including reconstruction, surface alloying, and other defects often present in metals supported on (111) surfaces.

Brillouin zone integrations during geometry optimization were carried out with a (3×3×1) k-point sampling [74] for the (6×6) surface model and (1×1×1) k-point sampling for the larger surface cells. We used a finer mesh of k-points to calculate energetic and electronic properties: (5×5×1) for the (6×6) surface models and (3×3×1) for the larger surface cells. The employed energy-cut-off, k-point meshes, and surface models provide converged results at a reasonable computational cost [27]. In the models, all M atoms were initially placed above ideal 1) fcc, 2) bridge, or 3) hcp sites on the (111) surfaces. During the geometry optimizations, the two “bottom” atomic layers of the surface models were held fixed at the calculated bulk lattice structure of Au [32], while the remaining atoms were allowed to relax until residual forces were less than 2×10−4 eV/pm.

3. Results And Discussion

In this section, we first discuss the possible atomic structures of the M37 nanoislands deposited on M(111) and Au(111) surfaces. These studies help to understand better the effect of the Au-substrate on the properties of the Mn nanoislands. Later, we focus on the atomic structures of M37 nanoislands with the lowes energy on Au(111) and discuss their geometric and electronic properties. To conclude this section, we explore size effects on the atomic structures of Cu, Pd, Ag, Pt, and Au nanoislands on Au(111).

3.1. Atomic structures of M37 nanoislands on M(111) and Au(111)

We are interested in two key aspects that characterize the atomic structures of single-layer nanoislands of metal M on (111) surfaces: i) the locations of the M atoms on the surface (near fcc, hcp, bridge, or ontop sites) and ii) how such location differs for atoms at the edges and center of the nanoislands. We calculated the in-plane relative displacement of each M atom from ideal fcc sites on the (111) surfaces to examine the optimized atomic structures of the nanoislands. The relative displacement from fcc sites allows a straightforward identification of the location of the atoms; relative displacement values of 0, 0.5, and 1 correspond to the ideal fcc, bridge, and hcp sites on the (111) surface. Mapping the relative displacement from fcc sites on top of the relative radial position of the M atoms allows examining the location of atoms at the edges and center of the nanoislands.

Figure 1 shows the relative displacement for M atoms as a function of relative radial position in the optimized atomic structures of one representative nanoisland on the M(111) and Au(111) surfaces. For nanoislands deposited on homonuclear surfaces, M37/M(111), there are two possible atomic structures: i) M atoms are near fcc sites, and ii) M atoms are near hcp sites. As shown in Figure 1 for Pd37/Pd(111), atoms at the center of the nanoislands are located on fcc and hcp sites, but atoms at the edges are displaced from the fcc and hcp sites. In general, the structures of nanoislands deposited on homonuclear surfaces are not pseudomorphic as previously reported [18] for Ag nanoislands on Ag(111); see Figure S1 in the supplementary material (SM) section for results of nanoislands of Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au deposited on their homonuclear surfaces. On Au(111), the nanoislands are not pseudomorphic neither [27,30]. The results in Figure 1 for Pd37 on Au(111) show three possible atomic structures: i) atoms locate near fcc and bridge (we labeled this structure as f-b from now on), ii) hcp and bridge (labeled as h-b), and iii) fcc, bridge, and hcp (labeled as f-b-h) sites. Note that the f-b (or h-b) and f-b-h atomic structures differ on the location of atoms that are near bridge sites on Au(111); f-b (or h-b) has bridging atoms mainly near the edges of the nanoislands; see Figure 1d and Figure 1f. The f-b-h atomic structures, on the other hand, have bridging atoms near the edges and the center of the nanoislands; see Figure 1e. Nanoislands of Pt37 on Au(111) also show similar structures; see Figure S2 and S3 in supplementary material for their optimized atomic structures. An important aspect to point out is that the atomic structures of Cu37/Au are generally like those of Pd37/Au and Pt37/Au; see Figure S2 in the supplementary material. However, a closer inspection shows that all atomic structures of Cu37/Au have Cu atoms in the center and edges of the nanoislands located on fcc, hcp, and bridge sites; see Figure S3 in the supplementary material. The optimized atomic structures of Ni37, Rh37, and Ir37 on Au(111) are nonplanar, in contract to the Cu37, Pd37, Ag37, and Pt37 nanoislands; the atoms in Ni37, Rh37, and Ir37 nanoislands are squeezed out, resulting in structures with a buckling three times larger than that of the Cu37, Pd37, Ag37, and Pt37 nanoislands on Au(111) (see Figure S2 and Table S2 in the supplementary material). The Ni37, Rh37, and Ir37 nanoislands on Au(111) have atomic structures like Cu37/Au; see Figure S3 in the supplementary material.

Figure 1.

Figure 1.

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Relative displacement from ideal fcc sites as a function of the relative radial position of Pd atoms in the optimized structures of Pd37 nanoislands on the (a-c) Pd(111) and (d-f) Au(111) surfaces. Results are shown for Pd37 nanoislands where atoms are located near (a,d) fcc and bridge, (e) fcc, bridge, and hcp, and (b,c,f) hcp and bridge sites on the (111) surfaces. We labeled these structures as f-b, f-b-h, and h-b. The inserts in panels (a) and (b) show the relative distance (displacement) of the hcp site from the fcc site on a (111) surface and the relative radial distance in the circle, respectively. Relative displacement values of 0, 0.5, and 1 correspond to the fcc, bridge, and hcp sites on the (111) surface. Relative radial values of 0 and 1 correspond to the center and edge regions of the model nanoislands. Note that the structures f-b (or h-b) and f-b-h in Pd37/Au(111) have bridging atoms near the edges and center of the nanoislands, respectively.

Figure 2a displays the energies of the optimized atomic structures of M37 nanoislands deposited on M(111) surfaces. The results in Figure 2a show that for most metals deposited on homonuclear surfaces, there is an energy separation between the atomic structures with atoms near fcc and hcp sites. Only for Cu37, Ag37, and Au37, the energy separation is small, below 1 kJ/mol per atom. For M37 nanoislands on the Au(111) surface, the energy separation between possible atomic structures is small, 1-2 kJ/mol per atom in most cases (Figure 2b). A few observations in Figure 2b is worth mentioning. First, Ag37, Pt37, and Au37 nanoislands on Au(111) only have two stable structures, f-b and h-b in Ag37 and Au37, and f-c and f-b-h in Pt37. Second, the energy separations found for Ni37, Rh37, and Ir37 on Au(111) come mainly from the different atoms squeezed out in these nanoislands; see Figure S2 in the supplementary material. Third, the energy separations for the atomic structures of Cu37/Au are small, below 1 kJ/mol per atom, because all three atomic structures have Cu atoms on fcc, hcp, and bridge sites on Au(111); see Figure S3 in the supplementary material. Finally, the low energy atomic structures of Pd37 and Pt37 on Au(111) are different, f-b for Pd37 and f-b-h for Pt37, which could come from the strong Pt-Pt bond and the larger Au tensile strain effects on the structure of Pd than Pt nanoislands [30].

Figure 2.

Figure 2.

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Energies (per atom) of the optimized atomic structures of M37 nanoislands deposited a) M(111) and b) Au(111), M = Ni, Cu, Rh, Pd, Ag, Ir, Pt, Au. The labels f-b, h-b, and f-b-h correspond to M37 nanoislands where atoms are located near fcc and bridge, hcp and bridge, and fcc, bridge, and hcp sites on Au(111); see Figure 1. Energies are given relative to the total energy of the f-b structure. Numerical values are provided in Tables S1 and S2 in the supplementary material.

3.2. The geometry of single-layer M37 nanoislands on M(111) and Au(111)

Figure 3a shows the deviation of the average M-M nearest-neighbor distances of M37 in the gas phase and M37 nanoislands supported on M(111). The deviation is provided from the M-M distances in bulk M. The average M-M distance in the free-standing clusters is over 4% shorter than the M-M distance in bulk M. The lowering of the coordination numbers (CN) in the free-standing clusters results in compressive stress [15,16]. For M37 on M(111), the M-M distances in all nanoislands are 1% to 3% shorter than in bulk M.

Figure 3.

Figure 3.

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Deviation (in %) of the average M-M nearest-neighbor distances for a) M37 in the gas phase and M37 nanoislands on M(111) surfaces, and b) the M37 nanoislands on the Au(111) surface. In panel a), the deviation of the M-M distances is from the M-M distance in bulk M. In the case of panel b), the deviation of the average M-M distances is from the average M-M distance in the M37 nanoislands on the M(111) surfaces. Numerical values are provided in Tables S1, S2, S3, and S4 in the supplementary material.

Figure 3b shows the deviation of the average M-M nearest-neighbor distances of M37 nanoislands supported on Au(111) from the average M-M distances in M37 nanoislands supported on M(111). The M-M distances in M37 on Au(111) show interesting results. First, the average Cu-Cu distance is over 4% longer in CU37/AU than CU37/CU, showing the tensile strain of Au over CU37. Au-tensile strain effects are also found for Pd37/Au and Ag37/Au, where the average Pd-Pd and Ag-Ag distances are 1.3% and 0.5%, respectively, longer than the values in the corresponding M37/M. On the other hand, systems like Rh37, Ir37, and Pt37 supported on Au(111) show M-M distances over 1% shorter than in M37/M. The Au(111) substrates have a much smaller effect on the structure of Rh37, Ir37, and Pt37 nanoislands. Note that the results in Figure 3b for M37/Au correspond to the atomic structures of the M37 nanoislands with the lowest energy. However, the average M-M nearest-neighbor distances are similar for the other atomic structures; see Table S2 and S3 in the supplementary material

Figure 4a shows the buckling in the M37 nanoislands supported on the M(111) and Au(111) surfaces. In Figure 4b, the buckling in the first layer of the M(111) and Au(111) surfaces is shown. The buckling quantifies the corrugation of the surface. The M37 nanoislands on M(111) have a small buckling, below ~10 pm, indicating that the nanoislands are almost planar. In the case of the first layer of the M(111) surface, the buckling is also small; only Pt(111) and Au(111) display buckling values above 10 pm. In contrast, the buckling in the M37 nanoislands on Au(111) is generally higher, particularly for Rh37 and Ir37, where the buckling effects are readily appreciated; see Figure S2 in the supplementary material. The results in Figure 4 for M37 correspond to the atomic structures of the M37 nanoislands with the lowest energy. However, the buckling are similar to the other structures; see Table S2 and S3 in the supplementary material.

Figure 4.

Figure 4.

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Buckling in the a) M37 nanoislands on the M(111) and Au(111) surfaces, and b) the first layer of the M(111) and Au(111) surfaces. Numerical values are provided in Tables S1 and S2 in the supplementary material.

3.3. Electronic properties of single-layer M37 nanoislands on M(111) and Au(111)

Figure 5 shows the average energy of the d-band center of the M37 nanoislands on the M(111) and Au(111) surfaces relative to the Fermi level of the system. In general, the d-band centers of the M37 nanoislands supported on M(111) are relatively like those on Au(111). The energy of the d-band center of metal-supported metal nanoislands depends on multiple factors, including strain effects, vertical ligand effects, and lateral ligand effects [27]. As we showed in Sec. 3.1, M37 nanoislands on Au(111) do not form pseudomorphic structures. Thus, strain effects on the d-band center can be expected to be relatively small for the M37 nanoislands. Indeed, the d-band centers of the majority of the M37 nanoislands on Au are only ~0.3 eV closer to the Fermi energy of the system than the M37 nanoislands on M(111), see Figure 5b. The difference of ~0.3 eV between the d-band centers of M37 on Au(111) and M(111) could come from strain and vertical ligand effects. Strain effects, however, should be relatively small because the average M-M distances in M37/Au(111) and M37/M(111) differ by less than 12 pm. Thus, the difference of ~0.3 eV comes mainly from the vertical ligand effects associated with the heterogeneous bonding of M37 on Au. The results in Figure 5 for M37 correspond to the atomic structures of the M37 nanoislands with the lowest energy. However, the d-band center positions are similar for the other configurations; see Table S2 and S3 in the supplementary material.

Figure 5.

Figure 5.

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The average energy of the d-band center of a) M37 nanoislands on M(111) and Au(111) and b) average change in the d-band center of M37 when going from M(111) to Au(111). The d-band center energy is given relative to the Fermi level of the system. Numerical values are provided in Tables S1 and S2 in the supplementary material.

3.4. Size effects in the atomic structures of Cu, Pd, Ag, Pt, and Au nanoislands on Au(111)

The results discussed above suggest three possible atomic structures for nanoislands of a few nanometers deposited on Au(111). The work of Jalkanen et al. [19] using EAM potentials shows that the atomic structure of single-layer nanoislands of Cu on Pd(111) changes with the size of the nanoislands. We explored size effects for the hexagonal Cu, Pd, Ag, Pt, and Au nanoislands on Au(111). We focus on these nanoislands because those of Ni, Rh, and Ir deposited on Au(111) are nonplanar, and the study of such systems is outside the scope of the present work. Single-layer nanoislands of Cun, Pdn, Agn, Ptn, and Aun (n = 1, 7, 19, 37, 61, 91, and ∞) were simulated on Au(111) to explore size effects. The Cun, Pdn, Agn, Ptn, and Aun nanoislands were initiated with all atoms located on either fcc, bridge, or hcp positions on the Au(111) surfaces. After geometry optimization, the nanoislands ended with atomic structures like those shown in Figure 1, where atoms at the edges or center of the nanoisland are near bridge sites on Au(111). The Agn nanoislands on Au(111) ended with either the f-b or h-b atomic structures; the f-b-h structure was stable for these nanoislands.

Figure 6 shows the relative energy of the atomic structures of Cun, Pdn, Agn, Ptn, and Aun nanoislands on Au(111). The relative energy of the atomic structures shows some worth mentioning results. First, note the small energy separation between possible atomic structures of nanoislands on Au(111), of the order of 1 to 3 kJ mol−1 atom−1. These results point to the challenges of performing quantitative studies of the energetic properties of metal-supported nanoislands with DFT methods [75]. Second, Ag nanoislands show only a slight variation with size for the energy separation of the f-b and h-b atomic structures. These results come from the small interatomic distance mismatch of nanoislands of Ag on Au(111); 290 pm in Ag37 versus 294 pm for the Au surface (Tables S1 and S4 in the supplementary material).

Figure 6.

Figure 6.

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Energy of a) Agn and Aun, and b) Cun, Pdn, and Ptn (n = 19, 37, 61, 91 and ∞) on Au(111). The labels h-b and f-b-h correspond to structures with atoms located on hcp and bridge sites and fcc, bridge, and hcp sites on Au(111); see Figure 1. The f-b-h structures were not stable for Agn/Au. Energies are given relative to the f-b structures. Numerical values are provided in Table S6 in the supplementary material.

A third result, and likely the most significant one, is the size dependence of the relative stability of the atomic structures for nanoislands of Cu, Pd, Pt, and Au on Au(111). The results in Figure 6 shows three different behaviors for the nanoislands of various size. First, semi-nanoislands, with less than 19 atoms of Cu, Pd, Pt, and Au on Au(111), form the f-c structure, where atoms are located mainly near fcc and bridge sites on Au(111); see Table S6 in the supplementary material. Second, the various atomic structures (labeled as f-b, h-b, and f-b-h) are close in energy for the largest nanoislands that were studied, those with 91 atoms. However, the atomic structures of those nanoislands are significantly different; see Figure S4 and Figure S5 in the supplementary material for the atomic structures and relative displacement from ideal fcc sites for Cu91, Pd91, Pt91, and Au91 on Au(111). Third, the results show that the relative energetics of the atomic structure of nanoislands with 19 to 61 atoms are different for nanoislands of Cu, Pd, Pt, and Au on Au(111). Nanoislands with 19 to 37 atoms of Cu on Au(111) form the f-b-h structures, where atoms are located near fcc, hcp, and bridge sites on Au(111). The results for Cu contract with those of Jalkanen et al. [19] Accordingly, single-layer nanoislands of Cu on Pd(111) with less than 41 Cu atoms have atomic structures where all Cu atoms are on fcc sites. The difference could come from the use of different substrates (Au vs. Pd), but it could also reflect the limitation of the EAM potentials to simulate nanostructures. Finally, it is worth mentioning the case of nanoislands of Au on Au(111). Nanoislands with less than 61 atoms Au on Au(111) form atomic structures where atoms are mainly near fcc and bridge sites on Au(111). However, for Au-nanoislands with 91 atoms on Au(111), the atomic structures with Au atoms near fcc, bridge, and hcp become energetically possible.

4. Summary

We have used density functional theory to study the atomic structure of single-layer metal nanoislands supported on metal surfaces. Two types of surface systems were explored: nanoislands supported on homonuclear and heteronuclear surfaces. The atomic structures of small single-layer nanoislands of metal M (M = Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au) were explored on M(111) and Au(111) surfaces. The key findings of our study are i) nanoislands on their homonuclear surfaces are planar, but not fully pseudomorphic; ii) nanoislands of Cu, Pd, Ag, Pt, and Au have planar structures on Au(111), but those of Ni, Rh, and Ir are nonplanar; iii) nanoislands of Cu, Pd, Pt, and Au on Au(111) with a diameter below 3 nm can have one of a few distinct atomic structures, and iv) the relative stability of these atomic structures depends on the size and nature of the Au-supported nanoparticles.

Supplementary Material

1

Highlights.

  • Nanoislands on their homonuclear surfaces are planar, but not fully pseudomorphic.

  • Nanoislands of Cu, Pd, Ag, Pt, and Au have planar structures on Au(111), but those of Ni, Rh, and Ir are nonplanar.

  • Nanoislands of Cu, Pd, Pt, and Au on Au(111) with a diameter below 3 nm can have one of a few distinct atomic structures.

  • The relative stability of the atomic structures depends on the size and nature of the Au-supported nanoparticles.

Acknowledgments

This project was supported by the “Fondo Institucional para el Desarrollo de la Investigación (FIDI 2019-2020)” of the University of Puerto Rico at Cayey. T.C.F.F. was supported by the National Aeronautics and Space Administration (NASA) Training Grant No. NNX15AI11H. The content is solely the responsibility of the authors and does not necessarily represent the official views of NASA. Calculations were performed on the computing facility at the University of Puerto Rico at Cayey, supported in part by the National Institute of General Medical Sciences of the National Institutes of Health through Grant NIH NIGMS/INBRE P20GM103475-15. Its contents are solely the responsibility of the authors and do not necessarily represent the official view of the NIGMS or NIH.

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Footnotes

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Supplementary Material

See supplementary material for the tables with numerical values for the calculated geometric, energetic, and electronic properties of the nanoislands supported on Au(111).

Declaration of interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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