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We present an ab initio molecular dynamics study of the atomic and electronic structure of SbN (N=2-8 and 12) clusters within the local density approximation and pseudopotential representation of the electron-ion interaction. Simulated annealing calculations have been done for 6-, 7-, 8- and 12-atom clusters. While for Sb4 a bent rhombus is about 2 eV higher in energy than a regular tetrahedron, we find that it plays an important role in the structure of larger clusters. For Sb8 we obtain two weakly interacting tetrahedra to be of lowest energy. However, this is nearly degenerate with a bent rhombus interacting with a distorted tetrahedron. Further, our calculations suggest a bent rhombus based structure for Sb 12 cluster indicating the observation of Sb4n clusters in Sb vapor condensation cell to be due to abundance of Sb4 clusters. A large gap is found to exist between the highest and the next occupied Kohn-Sham eigenvalues of the lowest energy isomers of 3-, 5- and 7-atom clusters. This is in agreement with the abundance of cations of these clusters in the laser ablation experiments. {\textcopyright} 1995 American Institute of Physics.

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The Journal of Chemical Physics

Ab initio molecular dynamics study of antimony clusters

Lectures on Methods of Electronic Structure Calculations

Atomic and Electronic Structure of Clusters From Car-Parrinello Method

The electronic structure and relative stability of icosahedral Al12M (M=transition metal) clusters have been studied using the density functional theory within the local spin density approximation. Our calculations predict large binding energies for clusters with M atom in the middle of a d series in agreement with the occurrence of Al12W phase in these alloys and provide an insight into the understanding of the stability of AlM quasicrystals. {\textcopyright} 1994 The American Physical Society.

Physical Review B

Electronic structure and relative stability of icosahedral Al-transition-metal clusters

Supercomputing for Scientific Visualisation: Proceedings of the Seminar on {\ldots}

SUPERCOMPUTING IN AB-INITIO STUDIES OF MATERIALS

World Science, Singapore

Lectures on methods of electronic structure calculations

A model for the decagonal phase of the Al13Fe4 system is proposed. The electronic structure is calculated within the tight-binding method. Results for the local and the integrated electronic density of states at particular sites are presented.

Journal of Physics: Condensed Matter

Electronic structure of a quasicrystalline model for Al13Fe 4

The electronic and atomic structure of Sb4 and Sb8 clusters is studied using the ab initio molecular dynamics method in the local density approximation. While for Sb4 a regular tetrahedron is about 2.0 eV lower in energy than a bent rhombus, for Sb8 two weakly interacting tetrahedra lie only 0.117 eV lower in energy than a bent rhombus interacting with a stretched tetrahedron, indicating the importance of the bent rhombus structure for larger clusters. The binding energy of Sb8 relative to two noninteracting tetrahedra is about 0.5 eV. These results are in excellent agreement with the experimental data. {\textcopyright} 1993 The American Physical Society.

Electronic and atomic stuctures of Sb4 and Sb8 clusters

We present results of the electronic structure and stability of some forty valence electron icosahedral Al12X (X=B, Al, Ga, C, Si, Ge, Ti and As) clusters within the local spin density functional theory. It is shown that the stability of the Al13 cluster can be substantially enhanced by proper doping. For neutral clusters, substitution of C at the center of the icosahedron leads to the largest gain in energy. However, Al12B- is the most strongly bound in this family. These results are in agreement with the recent experiments which also find Al12B- to be highly abundant. {\textcopyright} 1993 The American Physical Society.

Physical Review Letters

Enhanced stability of magic clusters: A case study of icosahedral Al12X, X=B, Al, Ga, C, Si, Ge, Ti, As

We present a tight-binding model for the electronic structure of solid C60 using four (one 2s and three 2p) orbitals per carbon atom. The model has been developed by fitting the tight-binding parameters to the ab initio pseudopotential calculation of Troullier and Martins (1992) in the face-centred cubic (Fm3) phase. Following this, calculations of the energy bands and the density of electronic states have been carried out as a function of the lattice constant. Good agreement has been obtained with the observed lattice-constant dependence of Tc using McMillan's formula. Furthermore, calculations of the electronic structure are presented in the simple cubic (Pa3) phase.

Empirical tight-binding parameters for solid C60

International Centre for Theoretical Physics

ARE Sb4n (n&gt; 1) CLUSTERS WEAKLY INTERACTING TETRAHEDRA?

Compound fullerenes

Ab-initio calculations 1 for K 3 C 60 indicate that the general features of the energy bands within LDA remain nearly unchanged as compared to C 60 . In the electronphonon pairing mechanism of superconductivity in these materials, the variation in T c has been attributed to changes in the lattice constant 2 which affects N(E F ). We have therefore fitted the valence and conduction bands of the fcc C60, obtained by Troullier and Martins 3 from an LDA plane wave basis calculations, with a tight binding model and studied the energy bands as a function of the lattice constant. As the overlap between orbitals on neighbouring balls is small, the band width is found to decrease by about 30% in going from K 3 C 60 to Rb 2 CsC 60 . The density of states, thus, obtained is used to estimate variation in T c from McMillan's formula. These results are in good agreement with experimental data. Calculations of the energy bands are also presented for the low temperature [Formula: see text] structure.

International Journal of Modern Physics B

A Tight Binding Model for The Electronic Structure of FCC and SC C 60

Proceedings of the Adriatico Research Conference on Clusters and Fullerenes Trieste, Italy 23-26 1992 - Preface

Ab Initio pair potentials

Intern. j. of mod. physics, appl

Proceedings..., Trieste, 23-26 June 1992

From studies on some clusters of metals and semiconductors, there appear some similarities in the structure of clusters with a given number of atoms and having the number of valence electrons corresponding to a shell closing, Here we present results of the atomic and electronic structure of a few other clusters with 20 and 40 valence electrons, namely Sb 4 , Sn 5 and Sb 8 using the density functional molecular dynamics method. We suggest that the similarities in the structure and deviation from them may help to understand bonding characteristics in clusters and its evolution to bulk behaviour. Our results on Sb 8 cluster are preliminary but indicate that above room temperature its structure is two weakly interacting tetrahedra which is in general agreement with the observation of predominently antimony tetramers at T>300 K.

STRUCTURE OF s-p BONDED METAL CLUSTERS WITH 8, 20 AND 40 VALENCE ELECTRONS

The authors use the method of Mobius transformation introduced by Chen (1990) to obtain pair potentials for FCC metals from first-principles total energy calculations. The derivation is exact for radial potentials and it converges much faster than the earlier reported method of Carlsson-Gelatt- Ehrenreich (1980). They have tested this formulation for Cu using the tight binding representation of the linear muffin-tin orbital method. Their results agree with those obtained by Carlsson and co-workers and qualitatively with the other Morse-type pair potentials derived from effective medium theories.

Ab initio pair potentials for FCC metals: An application of the method of Mobius transformation

Solid state communications

M{\"{o}}ssbauer study of Al 13 Fe 4

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. {\textcopyright} 1991 Springer-Verlag.

Zeitschrift f{\"{u}}r Physik D Atoms, Molecules and Clusters

A density functional molecular dynamics study of the bonding and stability of Mgn clusters (n=2-13)

The structure, growth and bonding nature of Mgn (n=213) clusters is studied using the density-functional molecular-dynamics method and the simulated annealing technique within the local-density approximation. We find a tetrahedron and a trigonal prism as two important constituents of the structure of Mg clusters to which atoms can be added by capping the faces. Mg13 is neither an icosahedron nor a cuboctahedron. The lowest-energy structure of Mg13 that we obtained from our simulated annealing can be considered as fusion of Mg9 and Mg4 clusters. This is nearly degenerate with the relaxed hcp structure and suggests the possibility of a path for transition to hcp structure for bigger clusters. We find Mg4 and Mg10 to be the magic clusters, which is in general agreement with the predictions of the jellium model of metal clusters. However, calculations of the charge densities, the p character and the gap between the highest occupied and the lowest unoccupied states suggest the presence of mixed bonding character in Mg clusters and an oscillatory and slow convergence to bulk metallic behavior. {\textcopyright} 1991 The American Physical Society.