The 3Π0u ← X 3Δ1g band system of jet‐cooled Ti2

Theoretical study on structural evolution, photoelectron and vibrational spectra, and thermochemistry properties of neutral, anionic and di-anionic titanium-doped tin (TiSnn0/-/2- (n = 4-17)) nanoalloy clusters

The structural evolution, chemical stability, electronic and vibrational properties, as well as charge transfer and bonding character of TiSnn0/-/2- (n = 4-17) clusters have been performed with density functional theory calculations using ABCluster search technique. Structurally, it is found that the growth patterns prefer three kinds of absorbed stages from polygonal bipyramidal configuration for n = 4-6, to absorbing additional Sn on the adjacent surfaces of pentagonal bipyramid unit from n = 7-12, and finally to the TiSn130/-/2- cluster as the first foundational architectures, of which the encapsulated cage structure is formed when n = 11. The simulated PES spectra agree with available experiments. More interestingly, the neutral TiSn16 cluster not only possesses the high thermodynamic and relative stability but also preferable photochemical reactivity, that can be further explained by superatom features and delocalized multi-center bonds (AdNDP), while the strong p-d hybridization between Ti atom and Sn unit plays an important role in the stabilities of clusters, making it as the most suitable building units. In addition, the UV-Vis absorption spectra of TiSn16 are discussed, and the main transitions of crucial excited states are analyzed in detail. The Infrared and Raman vibrational characteristic peaks of all these neutral and charged species are properly assigned, of which the TiSnn0/-/2- (n = 10-17) clusters possess degenerating deformation mode of Ti atom wagging in Sn cage framework (Infrared active) and breathing mode of Sn cage framework (Raman active). All these findings will provide a further understanding for the nanoalloy cluster as the most suitable building block with further development as a potential optoelectronic material.

Structural evolution and electronic properties of neutral and anionic TiASil (A = Sc, Ti; l ≤ 12): relatively stable TiASi4 as a structural unit

Molecular orbitals (MO) and the HOMO–LUMO energy gaps (HLgs) of neutral TiASi4 clusters (A = Sc, Ti).

Role of metcar on the adsorption and activation of carbon dioxide: a DFT study

Metallocarbohedrenes or metcars belong to one of the classes of stable nanoclusters having a specific stoichiometry. In spite of the available theoretical and experimental studies, the structure of pristine Ti8C12 metcar is still uncertain. We study the geometric structure of a titanium metcar, Ti8C12, together with its electronic properties and chemical activity towards adsorption and activation of CO2 molecule by means of density functional theory. Our results suggest that the CO2 molecule is strongly adsorbed and undergoes a significantly high degree of activation onto the Ti8C12 metcar. The migration of charge from titanium metcar to CO2 molecule attributes the high degree of activation of this molecule. In the infrared vibrational spectra for CO2 molecule adsorbed onto Ti8C12, we find a new signal which is absent in the corresponding spectra for gaseous CO2. In addition to adsorption energy, we also estimate the energy barrier for the dissociation of CO2 molecule to CO and O fragments on a Ti8C12 cluster. As a whole, this work reveals the ground state geometry of Ti8C12 metcar and highlights the role of this metcar in CO2 adsorption and activation, which are the key steps in designing potential catalysts for CO2 capture and its conversion to industrially valuable chemicals.

Metal-Metal (MM) Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc

This survey of metal-metal (MM) bond distances in binuclear complexes of the first row 3d-block elements reviews experimental and computational research on a wide range of such systems. The metals surveyed are titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc, representing the only comprehensive presentation of such results to date. Factors impacting MM bond lengths that are discussed here include (a) the formal MM bond order, (b) size of the metal ion present in the bimetallic core (M₂) ⁿ⁺, (c) the metal oxidation state, (d) effects of ligand basicity, coordination mode and number, and (e) steric effects of bulky ligands. Correlations between experimental and computational findings are examined wherever possible, often yielding good agreement for MM bond lengths. The formal bond order provides a key basis for assessing experimental and computationally derived MM bond lengths. The effects of change in the metal upon MM bond length ranges in binuclear complexes suggest trends for single, double, triple, and quadruple MM bonds which are related to the available information on metal atomic radii. It emerges that while specific factors for a limited range of complexes are found to have their expected impact in many cases, the assessment of the net effect of these factors is challenging. The combination of experimental and computational results leads us to propose for the first time the ranges and "best" estimates for MM bond distances of all types (Ti-Ti through Zn-Zn, single through quintuple).

Thermodynamically accessible titanium clusters TiN, N = 2–32

We have performed a genetic algorithm search on the tight-binding interatomic potential energy surface (PES) for small Ti_N (N = 2–32) clusters.

Stability and bonding of the multiply coordinated bimetallic boron cycles: B8M22−, B7NM2and B6C2M2with M = Sc and Ti

A theoretical investigation of the geometry, stability and aromaticity of boron clusters doped by two Sc and Ti atoms was carried out using DFT calculations.

MOLECULAR DYNAMICS STUDY OF Tin, Vn AND Crn CLUSTERS

Using a Morse type pair potential, molecular-dynamics simulations have been performed to investigate the atomic geometries, growing patterns, structural stabilities, energetics and magic sizes of Ti n, V n and Cr n (n = 2-50) clusters. Following rearrangement collision of the atom–cluster system in fusion process, and absorbing their energies step by step down to 0 K, possible optimal equilibrium geometries of the clusters have been generated to tackle the structural determination problem. This approach serves an efficient alternative to the growing path identification and the optimization techniques. It has been found that titanium, vanadium and chromium clusters prefer to form three-dimensional compact structures in the determined configurations and the appearances of medium sizes are, in general, five-fold symmetry on the spherical clusters. Moreover, relevant relations between atomic arrangements in the clusters and the magic sizes have been observed.

Matrix Isolation Infrared Spectroscopic and Theoretical Study of Group IV Metal Oxide Clusters: M2O2 and M2O4

Dinuclear titanium, zirconium, and hafnium oxide clusters, M2O2 and M2O4 (M = Ti, Zr, Hf) have been prepared and characterized by matrix isolation infrared spectroscopy and quantum chemical calculations. The M2O2 clusters were formed through the reactions of metal dimers and O2 in solid argon upon sample annealing. Theoretical calculations indicate that the Ti2O2 cluster has a singlet ground state with a nonplanar cyclic C(2v) structure with a strong Ti-Ti bond, while the Zr2O2 and Hf2O2 clusters have planar cyclic structures. The M2O4 clusters were characterized to have a closed-shell singlet ground state with a nonplanar C2h symmetry, which were formed from the dimerization of the metal dioxide molecules.

Computational Study of Multiple-Decker Sandwich and Rice-Ball Structures of Neutral Titanium−Benzene Clusters

Density functional theory calculations were applied to systematically and directly compare the relative energetic stability of multiple-decker sandwich and rice-ball structures for a variety of neutral Ti(m)Bz(n) clusters (m = 1-4, n = 1-5). Almost all structures favored the multiple-decker sandwich structure, as observed experimentally for early transition metals. The strength of each metal-benzene interaction averages 37 kcal/mol and remains relatively constant for sandwiches with three or more Ti atoms. The most stable smaller rice-ball structures did not have eta(6)-Bz bound to a single metal atom. Instead, the preferred coordination was having the plane of the benzene molecule parallel to a Ti(2) bond or a Ti(3) face, leading to some distortion of the benzene ring. The larger rice-ball structures, on the other hand, preferred to weaken the metal-metal bonds and retain eta(6)-Bz bound to a single metal atom, a structural motif shared with sandwiches.

Low-lying electronic states of the Ti2 dimer: Electronic absorption spectroscopy in rare gas matrices in concert with quantum chemical calculations

Absorption spectra were measured for Ti2 in Ne and Ar matrices. The spectra give evidence for several electronic transitions in the region between 4000 and 10 000 cm(-1) and provide important information about some excited electronic states of Ti2 in proximity to the ground state. The vibrational fine structure measured for these transitions allowed to calculate the force constants and the anharmonicity of the potential energy curves of the excited states, and to estimate changes in the internuclear Ti-Ti distances relative to the electronic ground state. The quantum chemical studies confirm the previously suggested (3)Delta(g) state as the ground state of Ti2. The equilibrium bond distance is calculated to be 195.4 pm. The calculated harmonic frequency of 432 cm(-1) is in good agreement with the experimental value of 407.0 cm(-1). With the aid of the calculations it was possible to assign the experimentally observed transitions in the region between 4000 and 10 000 cm(-1) to the 1 (3)Pi(u)<--(3)Delta(g), 1 (3)Phi(u)<--(3)Delta(g), 2 (3)Pi(u)<--(3)Delta(g), 2 (3)Phi(u)<--(3)Delta(g), and (3)Delta(u)<--(3)Delta(g) excitations (in the order of increasing energy). The calculated relative energies and harmonic frequencies are in pleasing agreement with the experimentally obtained values, with deviations of less than 5% and 2%, respectively. The bond distances estimated on the basis of the experimental spectra tally satisfactorily with the predictions of our calculations.

A density-functional study of Al-doped Ti clusters: TinAl (n=1–13)

Equilibrium geometries, stabilities, and electronic properties of TinAl (n = 1-13) clusters have been studied by using density-functional theory with local spin density approximation and generalized gradient approximation. The ground-state structures of TinAl clusters have been obtained. The resulting geometries show that the aluminum atom remains on the surface of clusters for n < 9, but is slowly getting trapped beyond n = 9, meanwhile, the Al atom exhibits a valent transition from monovalent to trivalent. The geometric effects and electronic effects clearly demonstrate the Ti4Al cluster to be endowed with special stability. The studies on the bonds indicate the change from ionic to metalliclike.