Ab initio molecular dynamics study of antimony clusters
22 Jun 1995-Journal of Chemical Physics (American Institute of Physics)-Vol. 102, Iss: 24, pp 9631-9637
TL;DR: In this article, 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 was studied.
Abstract: 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 Sb12 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 agreemen...
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TL;DR: In this article, a review of the microcanonical approach to thermodynamics is presented, with a focus on hot nuclei, hot atomic clusters, and gravitating systems, and their applications in physics.
232 citations
TL;DR: In this article, the electronic structure and chemical bonding of the pentapnictogen cluster anions, Pn5- (Pn = P, As, Sb, and Bi), were investigated using both photoelectron spectroscopy and ab initio calculations.
Abstract: The electronic structure and chemical bonding of the pentapnictogen cluster anions, Pn5- (Pn = P, As, Sb, and Bi), were investigated using both photoelectron spectroscopy and ab initio calculations. Well-resolved photoelectron spectra were obtained for the anions at several photon energies and were analyzed according to the theoretical calculations. The ground state of all the Pn5- species was found to be the aromatic cyclic D5h structure with a C2v low-lying isomer. We found that the C2v isomer gains stability from P5- to Sb5-, consistent with the experimental observation of the coexistence of both isomers in the spectra of Sb5-. The valence molecular orbitals (MOs) of the D5h Pn5- were analyzed and compared to those of the aromatic C5H5- hydrocarbon. The same set of π-MOs is shown to be occupied in the D5h Pn5- and C5H5- species, except that the MO ordering is slightly different. Whereas the three π-MOs in C5H5- all lie above the σ-MOs, the third π orbital (1a2‘ ‘ in Pn5-) lies below the σ-MOs. The stab...
90 citations
TL;DR: The first ab initio theoretical study of tetraantimony hexoxide (Sb4O6) is reported, and correction factors for the calculated vibrational frequencies were determined and compared.
52 citations
TL;DR: In this article, the authors studied the thermodynamics of microcanonical phase transitions of first and second order in systems which are thermodynamically stable in the sense of van Hove and showed how both kinds of phase transitions can unambiguously be identified in relatively small isolated systems of ∼ 100 atoms.
Abstract: The volume W of the accessible N-body phase space and its dependence on the total energy is directly calculated. The famous Boltzmann relation S = k * ln(W) defines microcanonical thermodynamics (MT). We study how phase transitions appear in MT. Here we first develop the thermodynamics of microcanonical phase transitions of first and second order in systems which are thermodynamically stable in the sense of van Hove. We show how both kinds of phase transitions can unambiguously be identified in relatively small isolated systems of ∼ 100 atoms by the shape of the microcanonical caloric equation of state 〈 T(E/N) ⌨ and not so well by the coexistence of two spatially clearly separated phases. I.e. within microcanonical thermodynamics one does not need to go to the thermodynamic limit in order to identify phase transitions. In contrast to ordinary (canonical) thermodynamics of the bulk microcanonical thermodynamics (MT) gives an insight into the coexistence region. Here the form of the specific heat c(E/N) connects transitions of first and second order in a natural way. The essential three parameters which identify the transition to be of first order, the transition temperature T tr, the latent heat q lat, and the interphase surface entropy Δs ssurf can very well be determined in relatively small systems like clusters by MT. It turns out to be essential whether the cluster is studied canonically at constant temperature or microcanonically at constant energy. Especially the study of phase separations like solid and liquid or, as studied here, liquid and gas is very natural in the microcanonical ensemble, whereas phase separations become exponentially suppressed within the canonical description. The phase transition towards fragmentation is introduced. The general features of MT as applied to the fragmentation of atomic clusters are discussed. The similarities and differences to the boiling of macrosystems are pointed out.
23 citations
TL;DR: In this paper, the geometries and vibrational properties of the low-lying electronic states of neutral and anionic of M3 (M = P, As, Sb, and Bi) were studied using the coupled-cluster singles, doubles, and noniterative triples (CCSD(T)) method as well as the density functional theory (B3LYP-DFT) method.
Abstract: The geometries and vibrational properties of the low-lying electronic states of neutral and anionic of M3 (M = P, As, Sb, and Bi) are studied using the coupled-cluster singles, doubles, and noniterative triples (CCSD(T)) method as well as the density functional theory (B3LYP-DFT) method. For P3-, the and states are almost degenerate. The state, however, turns out to be the lowest state for As3-, Sb3-, and Bi3-, and the adiabatic excitation energies of the state are 0.6, 0.9, and 1.0 eV, respectively. In the anionic trimers of all four elements, another singlet state, 1A1(C2v), is located about 0.3−0.4 eV above ; the energy gap between these states is compared to the splittings between the first two peaks in the photoelectron spectra of these anions. For all of the neutral trimers, the adiabatic and vertical energetic splittings between the Jahn−Teller components of the X2E‘ ‘ and 4E‘ states are calculated to be only 0.04−0.08 eV. Another quartet state, is 0.4 eV higher, almost equal, 0.2 eV lower, and 0.3...
20 citations
References
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Book•
01 Jan 1939
5,955 citations
TL;DR: In this paper, a simple way has been discovered to put model pseudopotentials, $V(\stackrel{\ensuremath{\rightarrow}}{\mathrm{r}}), into a form which reduces the number of integrals required for an energy-band calculation from ϵ(n+1) to ϵ (n+2) for each $l$ in the sum.
Abstract: A simple way has been discovered to put model pseudopotentials, $V(\stackrel{\ensuremath{\rightarrow}}{\mathrm{r}})={\ensuremath{\Sigma}}_{\mathrm{lm}}|{Y}_{\mathrm{lm}}〉{V}_{l}(r)\ifmmode\times\else\texttimes\fi{}〈{Y}_{\mathrm{lm}}|$, into a form which reduces the number of integrals of $V(\stackrel{\ensuremath{\rightarrow}}{\mathrm{r}})$ required for an energyband calculation from $\frac{\mathrm{mn}(n+1)}{2}$ to $\mathrm{mn}$ for each $l$ in the sum (where $n$ is the number of plane waves used in the expansion and $m$ the number of points in the Brillouin zone at which the calculation is performed). The new form may be chosen to improve the accuracy of the pseudopotential when used in other chemical environments.
4,301 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: In this paper, the borane-carborane structural pattern has been studied in a wide range of other compounds, including metal clusters, metal-hydrocarbon 7∼ complexes, and various neutral or charged hydrocarbons.
Abstract: Publisher Summary This is one of two articles in this volume that is concerned with the borane-carborane structural pattern. In the other, Williams has shown how the pattern reflects the coordination number preferences of the various atoms involved. The purpose of the present article is to note some bonding implications of the pattern, and to show its relevance to a wide range of other compounds, including metal clusters, metal-hydrocarbon 7∼ complexes, and various neutral or charged hydrocarbons. Boranes and carboranes may be regarded as cluster compounds in the sense defined by Cotton; they contain a finite group or skeleton of atoms held together entirely, mainly, or at least to a significant extent by bonding directly between those atoms, even though some other atoms may be associated intimately with the cluster. Examples of their structural pattern, however, can be found far beyond the confines of what is normally regarded as cluster chemistry, so this survey includes many systems not commonly referred to as clusters.
1,235 citations
TL;DR: In this paper, the main problems underlying the experimental study of particles with sizes between single atoms and the solid state have been solved: the formation of metal clusters, their individual detection, and the separation of beams with uniform cluster size.
Abstract: The main problems underlying the experimental study of particles with sizes between single atoms and the solid state have been solved: the formation of metal clusters, their individual detection, and the separation of beams with uniform cluster size. By inertgas condensation of metal vapors the clusters ${\mathrm{Sb}}_{1}$-${\mathrm{Sb}}_{500}$, ${\mathrm{Bi}}_{1}$-${\mathrm{Bi}}_{280}$, and ${\mathrm{Pb}}_{1}$-${\mathrm{Pb}}_{400}$ have been produced. The high intensity observed over the whole mass range henceforth allows a systematic size-dependent investigation of metal clusters.
308 citations