A density functional molecular dynamics study of the bonding and stability of Mgn clusters (n=2−13)
TL;DR: A study of the structure and the bonding nature of Mg clusters having 2 to 13 atoms has been made using the density functional molecular dynamics method within the local density approximation as mentioned in this paper.
Abstract: A study of the structure and the bonding nature of Mg clusters having 2 to 13 atoms has been made using the density functional molecular dynamics method within the local density approximation. The calculated lowest energy structures can be described in terms of a tetrahedron and a trigonal prism. Mg4 and Mg10 are magic clusters and Mg13 is neither an icosahedron nor a cuboctahedron. The bonding nature varies from atom to atom in a cluster and the transition from weakly bonded dimer to bulk like metallic behaviour is oscillatory and slow.
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TL;DR: The specific characteristics of the formation of atomic clusters partly generated far from equilibrium in the helium environment are summarized, with special emphasis on the optical response, electronic properties as well as dynamical processes which are mostly affected by the surrounding quantum matrix.
Abstract: The unique conditions forming atomic and molecular complexes and clusters using superfluid helium nanodroplets have opened up an innovative route for studying the physical and chemical properties of matter on the nanoscale. This review summarizes the specific characteristics of the formation of atomic clusters partly generated far from equilibrium in the helium environment. Special emphasis is on the optical response, electronic properties as well as dynamical processes which are mostly affected by the surrounding quantum matrix. Experiments include the optical induced response of isolated cluster systems in helium under quite different excitation conditions ranging from the linear regime up to the violent interaction with a strong laser field leading to Coulomb explosion and the generation of highly charged atomic fragments. The variety of results on the outstanding properties in the quantum size regime highlights the peculiar capabilities of helium nanodroplet isolation spectroscopy.
181 citations
TL;DR: The results of an extensive structural study of Na13, Mg13, Al13, and Si13 carried out with the Car-Parrinello method are reported in this paper.
Abstract: We report the results of an extensive structural study of Na13, Mg13, Al13, and Si13 carried out with the Car–Parrinello method. Several and mostly unforeseen noncrystalline structures are discovered to characterize the low portion of the potential energy surface. Crystalline structures are shown either to correspond to high‐energy local minima or to be highly unstable. The low‐energy structural pattern appears to change significantly from one element to the other. Specific characteristics as well as trends are discussed.
114 citations
TL;DR: There is a similarity in the N dependence of the HOMO-LUMO gap between the three metal clusters, it is much stronger between the two noble metal clusters and the magic number is explicitly defined with a new criterion in the framework of total energy calculations.
Abstract: The geometric and electronic structures of NaN, CuN, and AgN metal clusters are systematically studied based on the density functional theory over a wide range of cluster sizes 2≤N≤75. A remarkable similarity is observed between the optimized geometric structures of alkali and noble metal clusters over all of the calculated cluster sizes N. The most stable structures are the same for the three different metal clusters for approximately half the cluster sizes N considered in this study. Even if the most stable structures are different, the same types of structures are obtained when the metastable structures are also considered. For all of the three different metal clusters, the cluster shapes change in the order of linear, planar, opened, and closed structures with increasing N. This structural-type transition leads to a deviation from the monotonic increase in the specific volume with N. A remarkable similarity is also observed for the N dependence of the cluster energy E(N) for the most stable geometric structures. The amplitude of this energy difference is larger in the two noble metal clusters than in the alkali metal cluster. This is attributed to the contribution of d electrons to the bonds. The magic number is explicitly defined with a new criterion in the framework of total energy calculations. In the case of NaN, a semiquantitative comparison between the experimental abundance spectra [Knight et al., Phys. Rev. Lett. 52, 2141 (1984)] and the total energy calculations is carried out. The changing aspect of the Kohn–Sham eigenvalues from N=2 to N=75 is presented for the three different metal clusters. The feature of the bulk density of states already appears at N=75 for all of three clusters. With increasing N, the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap clearly exhibits an odd-even alternation and converges to 0. Although there is a similarity in the N dependence of the HOMO-LUMO gap between the three metal clusters, it is much stronger between the two noble metal clusters. The growth aspect of the d band below the Fermi level of the noble metal clusters with increasing N is presented. A good correspondence is observed in the d characteristic of the electronic states between the cluster composed of 75 atoms and the bulk metal. The similarities observed in the N dependence of the geometric structures and E(N)s originate from the similarity in that of the electronic structures.
82 citations
TL;DR: In this paper, the geometric and electronic structures of NaN, CuN, and AgN metal clusters are systematically studied based on the density functional theory over a wide range of cluster sizes 2=
Abstract: The geometric and electronic structures of NaN, CuN, and AgN metal clusters are systematically studied based on the density functional theory over a wide range of cluster sizes 2=
70 citations
TL;DR: In this paper, the divalent metals magnesium, cadmium, and zinc have been grown in ultracold helium nanodroplets and studied by high-resolution mass spectrometry, with a special emphasis on magnesium.
Abstract: Clusters of the divalent metals magnesium, cadmium, and zinc have been grown in ultracold helium nanodroplets and studied by high-resolution mass spectrometry, with a special emphasis on magnesium. The mass spectra of all materials show similar characteristic features independent of the chosen ionization technique - i.e., electron impact ionization as well as nanosecond and femtosecond multiphoton excitation. In the lower-size range the abundance distributions can be explained by an electronic shell structure. The associated electron delocalization - i.e., metallic bonding - is found to set in at about N=20 atoms. For Mg{sub N} we have resolved crossings of electronic levels at the highest-occupied molecular orbital which result in additional magic numbers compared to the alkali metals: e.g., Mg{sub 40} with 80 electrons. This specific electronic shell structure is also present in the intensity pattern of doubly charged Mg{sub N}. For larger clusters (N{>=}92) a coexistence of electronic shell effects and geometrical packing is observed and a clear signature of icosahedral structure is present beyond N{>=}147.
48 citations
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TL;DR: In this article, a unified scheme combining molecular dynamics and density-functional theory is presented, which makes possible the simulation of both covalently bonded and metallic systems and permits the application of density functional theory to much larger systems than previously feasible.
Abstract: We present a unified scheme that, by combining molecular dynamics and density-functional theory, profoundly extends the range of both concepts. Our approach extends molecular dynamics beyond the usual pair-potential approximation, thereby making possible the simulation of both covalently bonded and metallic systems. In addition it permits the application of density-functional theory to much larger systems than previously feasible. The new technique is demonstrated by the calculation of some static and dynamic properties of crystalline silicon within a self-consistent pseudopotential framework.
8,852 citations
TL;DR: In this article, a consistent set of pseudopotentials has been developed for the entire Periodic Table, and a scheme used to generate the numerical potentials, the fitting procedure, and the testing of the fit are discussed.
Abstract: Recent developments have enabled pseudopotential methods to reproduce accurately the results of all-electron calculations for the self-consistent electronic structure of atoms, molecules, and solids. The properties of these potentials are discussed in the context of earlier approaches, and their numerous recent successful applications are summarized. While the generation of these pseudopotentials from all-electron atom calculations is straightforward in principle, detailed consideration of the differences in physics of various groups of atoms is necessary to achieve pseudopotentials with the most desirable attributes. One important attribute developed here is optimum transferability to various systems. Another is the ability to be fitted with a small set of analytic functions useful with a variety of wave-function representations. On the basis of these considerations, a consistent set of pseudopotentials has been developed for the entire Periodic Table. Relativistic effects are included in a way that enables the potentials to be used in nonrelativistic formulations. The scheme used to generate the numerical potentials, the fitting procedure, and the testing of the fit are discussed. Representative examples of potentials are shown that display attributes spanning the set. A complete tabulation of the fitted potentials is given along with a guide to its use.
2,238 citations
TL;DR: The possibility of ellipsoidal distortions in free-electron metal clusters, analogous to the shape variations among atomic nuclei, was investigated with the use of a modified Nilsson Hamiltonian as discussed by the authors.
Abstract: The possibility of ellipsoidal distortions in free-electron metal clusters, analogous to the shape variations among atomic nuclei, is investigated with the use of a modified Nilsson Hamiltonian. In most cases, the predicted equilibrium shape is ellipsoidal rather than spherical, so that the spherical shells are divided into ellipsoidal subshells. A strong correlation is observed between the energy-level sequence of these subshells and the sequence of peaks in alkali-metal cluster mass spectra, indicating that metal clusters generally assume approximately ellipsoidal shapes.
522 citations