The systematic cluster growth (SCG) method is a biased structure search strategy based on a seeding process for investigating the structural evolution and growth pattern of transition metal clusters. ...In SCG, a set of initial structures with size
n
are constructed based on the equilibrium structures of the preceding
n
− 1 cluster isomers by adding a single atom at all inequivalent binding sites. This strategy requires a relatively low number of evaluations for global minima localization on the potential energy surface, allowing its application in first-principles calculations. The performance of SCG is tested by using the Lennard Jones (LJ) potential energy surface. The 93.7% of the best-known solutions for Lennard Jones clusters were found for
n
≤ 80 by using a relatively low number of local optimizations. Most importantly, by using SCG combined with DFT calculations (SCG-DFT), we revisit and provide the ground state structures and growth pattern for transition metal clusters TM
n
(where TM = Ti, Ni, Cu, Ag, Pt; and
n
= 6-14). The application of the code for doped clusters is also discussed. A detailed description of the present method for generating the structures of the clusters is provided.
The systematic cluster growth (SCG) method is a biased structure search strategy based on a seeding process for investigating the structural evolution and growth pattern of transition metal clusters.
The structure, electronic and reactivity properties of PtnCun (n = 1–7) clusters are investigated in the framework of density functional theory (DFT). The most stable forms of the clusters are ...obtained by a structure search procedure based in simulated annealing. The results show that the PtnCun cluster alloys adopt layered structure motifs with segregation of the Cu and Pt species. The total magnetic moments of the clusters adopt the low spin configuration. The bimetallic cluster reactivity is investigated by using the ionization potential, electron affinity, and the d-band center, respectively. The results show that the PtnCun clusters with (n = 5–7) have similar vIP and vEA parameters compared to the unary Pt clusters, but the d-band center is slightly higher suggesting an enhanced reactivity for the bimetallic clusters. On the other hand, the molecular electrostatic potential shows that the Cu species increase the available active sites on the cluster surface. The data on the infrared spectra of the clusters is also provided. These results are useful to understand the fundamental properties of Pt–M bimetallic alloys in the subnanometer region.
Formation of cluster-based materials requires a fundamental understanding of the resulting cluster aggregation processes. The Sn
Zintl-ion structure can be viewed as a building block featuring a ...spherical aromatic species, leading to a cluster gathering upon oxidative coupling and/or mediated by transition metals. Here, we evaluate the spherical aromatic properties of Sn
-Sn
, Ag(Sn
-Sn
)
and (η
-Sn
)Ag(η
-Sn
)
, as aggregates of two Sn
building units held together
oxidative coupling and mediated by a Ag(I) transition metal center. Our results from magnetic criteria of aromaticity show that the inherent spherical aromatic characteristics of the parent Sn
cluster are persistent in the overall aggregate where the enabled shielding cones ascribed to each Sn
unit are able to interplay between them, leading to an overlap of the shielding regions. Hence, the two approaches for bringing cluster units together are able to retain the inherent spherical aromatic features for each Sn
unit, leading to a cluster-based dimer where the parent properties remain. Thus, further cluster-based materials can be envisaged from aggregation upon oxidative coupling and/or mediated by transition metals, where the constituent building blocks retain their initial features, useful to guide the formation of more complex cluster-based aggregates.
In the present work, the lowest energy structures and electronic properties of Agn clusters up to n = 16 are investigated using a successive growth algorithm coupled with density functional theory ...calculations (DFT). In the literature, a number of putative global minimum structures for silver clusters have been reported by using different approaches, but a comparative study for n = 15–16 has not been undertaken so far. Here, we perform a comparative study using the PW91/cc-pVDZ-PP level to more precisely determine the optimal configuration. For Ag15, the most stable configuration is a four layered 1-4-6-4 stacking structure with C2v symmetry. For Ag16 a new most stable form is found with a 1-4-2-5-1-3 stacking structure in the singlet state, slightly more stable than the putative global minimum reported. By means of the electrostatic potential, the new putative global minimum has been found to be more reactive, and the active sites of the clusters were identified and confirmed with the interaction energy. The electronic and vibrational properties are found to be in good agreement with the available experimental data. Theoretical data on the infrared spectra of the clusters is also provided.
Formation of cluster-based materials requires a fundamental understanding of the resulting cluster aggregation processes. The Sn
9
4−
Zintl-ion structure can be viewed as a building block featuring a ...spherical aromatic species, leading to a cluster gathering upon oxidative coupling and/or mediated by transition metals. Here, we evaluate the spherical aromatic properties of Sn
9
-Sn
9
6−
, Ag(Sn
9
-Sn
9
)
5−
and (η
4
-Sn
9
)Ag(η
1
-Sn
9
)
7−
, as aggregates of two Sn
9
building units held together
via
oxidative coupling and mediated by a Ag(
i
) transition metal center. Our results from magnetic criteria of aromaticity show that the inherent spherical aromatic characteristics of the parent Sn
9
4−
cluster are persistent in the overall aggregate where the enabled shielding cones ascribed to each Sn
9
unit are able to interplay between them, leading to an overlap of the shielding regions. Hence, the two approaches for bringing cluster units together are able to retain the inherent spherical aromatic features for each Sn
9
unit, leading to a cluster-based dimer where the parent properties remain. Thus, further cluster-based materials can be envisaged from aggregation upon oxidative coupling and/or mediated by transition metals, where the constituent building blocks retain their initial features, useful to guide the formation of more complex cluster-based aggregates.
Formation of cluster-based materials requires a fundamental understanding of the resulting cluster aggregation processes.
The aggregation of halide atoms into gold clusters offers an interesting scenario for the development of novel metal-based cavities for anion recognition and sensing applications. Thus, further ...understanding of the different contributing terms leading to efficient cluster–halide aggregation is relevant to guide their synthetic design. In this report, we evaluate the formation of (Ph 3 PAu) 4 X 2 2+ and (Ph 3 PAu) 4 X 3+ species (X = Cl − , Br − , I − ) in terms of different energy contributions underlying the stabilization of the cluster–halide interaction, and the expected UV-vis absorption profiles as a result of the variation in frontier orbital arrangements. Our results denote that a non-planar Au 4 core shape enables enhanced halide aggregation, which is similar for Cl − , Br − , and I − , in comparison to the hypothetical planar Au 4 counterparts. The electrostatic nature of the interaction involves a decreasing ion–dipole term along with the series, and for iodine species, higher-order electrostatic contributions become more relevant. Hence, the obtained results help in gaining further understanding of the different stabilizing and destabilizing contributions to suitable cluster-based cavities for the incorporation of different monoatomic anions.
Understanding intercluster bonding interactions is important in the rational synthesis of building blocks for molecular materials. Such characteristics have been developed for coinage metal clusters ...resembling single-, double-, and triple-bonded species, coined as supermolecules. Herein, we extend such an approach for understanding main-group clusters, thus evaluating Pd
@E
clusters (E = Ge, Sn) involving the fusion of parent spherical aromatic Pd@E
building units. Our results indicate intercluster bonding provided by contribution from 2P and 1G shells centered at each building motif, leading to an overall bond order of 2.70 and 2.31 for Pd
@Ge
and Pd
@Sn
, respectively. In addition,
Sn-NMR patterns were evaluated to complement the experimental characterization of a single peak owing to the insolution fluxional behavior of Pd
@Sn
as three peaks owing to the three sets of unique Sn atoms within the structure. Magnetic response properties revealed that spherical aromatic characteristics from parent Pd@E
building units are retained in the overall Pd
@E
oblate cluster as two spherical aromatic units. Hence, the notion of superatomic molecules is extended to Zintl-ion clusters, favoring further rationalization for the fabrication of cluster-assembled solids.
In this work, we have performed a computational study on the structure and electronic properties for Be-doped Ptn (n = 1–12) clusters in the framework of density functional theory (DFT). The most ...stable structures of the clusters are obtained by a structure search procedure based in simulated annealing. The results show that the PtnBe clusters adopt compact structure motifs with Be situated at the edge sites while only in Pt11Be the Be atom occupies the center site. The energetic parameters showed that Pt5Be, Pt7Be and Pt10Be are the most stable ones. The PtnBe clusters with (n = 5–7) have similar vertical ionization potential (vIP) and vertical electron affinity (vEA) parameters compared to the unary Pt clusters, while Pt9Be and Pt11Be have the higher vEA values. In particular, the d-band center is slightly higher for the doped clusters, suggesting an enhanced reactivity. The σ-holes are found more remarkable for the doped clusters, which are situated in the Be dopant and low coordinated Pt sites. The data on the infrared spectra of the clusters is also provided and showed a significant blue shift due to the vibrational modes of the Be atom. These results are useful for understanding the fundamental properties of Be-doped Ptn clusters in the subnanometer region.
The experimental characterization of Cl@Si
endohedral clusters, featuring different ligands such as Cl@Si
H
(1) Cl@Si
H
Cl
(2), and Cl@Si
Cl
(3), provides insight into the variable encapsulation ...environment for chloride anions. The favorable formation of such species enables the evaluation of the encapsulation nature and the role of the inner anion in the rigidity of the overall cluster. Our results show a sizable interaction which increases as -66.7, -100.8, and -130.3 kcal mol
from 1 to 3, respectively, featuring electrostatic character. The orbital interaction involves 3p-Cl → Si
X
and 3s-Cl → Si
X
charge transfer channels and a slight contribution from London dispersion-type interactions. These results show that the inner bonding environment can be modified by the choice of exobonded ligands. Moreover,
Si-NMR parameters are depicted in terms of the chemical shift anisotropy (CSA), leading to a strong variation of the three principal tensor components (
,
,
), unraveling the origin of the experimental
Si-NMR chemical shift (
) differences along the given series. Thus, the Si
cage is a useful template to further evaluate different environments for encapsulating atomic species.
The development of well-defined atomically precise heteronuclear nanoclusters passivated by protecting ligands is presently a booming area, owing to the fact that doping well-known homonuclear ...nanostructures allows fine-tuning of their properties. Here, we explore by means of density functional theory calculations the possibility of doping the central gold atom in the classical Au13(dppe)5Cl23+cluster (1) by Os. Although both Au13(dppe)5Cl23+ and Os@Au12(dppe)5Cl2 have the same total number of electrons, we show that they are not isoelectronic within the formalism of the superatom model, being respectively an 8- and an 18-electron species. It results that they exhibit similar structures but present significantly different optical behaviors (ultraviolet/visible and circular dichroism). Similar results are obtained for the Ru and Fe relatives. Emission properties indicate some redshift of the T1→S1 decay with respect to Au13(dppe)5Cl23+, involving an equatorial distortion of the Au12Cl2 core in the T1 state, rather than the axial distortion afforded by 1. The sizable highest occupied molecular orbital–lowest unoccupied molecular orbital gaps found for the three doped species suggest that further experimental exploration of different stable doped species derived from the ligand-protected Au12Cl2 core should be encouraged.
