Ti Distance Research Articles

Lithium diffusion in La2/3–xLi3xTiO3 (x = 0.115) with 3D-ordered configurations

The present molecular dynamics study investigated lithium-ion diffusion in La2/3–xLi3xTiO3 (x = 0.115) with various structural configurations. The diffusion path and conductivity vary significantly depending on the configuration despite the constant lithium content. A highly-ordered configuration in the in-plane or out-of-plane directions tends to require higher activation energy for diffusion. In each configuration, the largest bottleneck area is found in the principal migration path with the short of Ti–Ti distance along the path. A comparison between various models revealed that the activation energy depends not on the size of the bottleneck area but on the dimensionality of lithium motion: a higher dimensionality such as three-dimensional diffusion lowers the activation energy.

Insight into the effect of support crystal form on semi-continuous oxidation of glycerol

In this work, two Pt catalysts using anatase and rutile as supports were prepared, and then the support effect on catalytic performance in glycerol oxidation was investigated. Different Pt/TiO2 catalysts exhibited not so negligible distinction on the product distribution. On one side, the C=O bonds of intermediate glyceraldehyde (GLYAD) highly dissociated in the form of bidentate species through C atom bonding to O atom and O atom bonding to Ti atom of rutile support, which largely promoted the transformation from GLYAD to glyceric acid (GLYA). While, in the case of anatase support, the adsorption form of C=O was monodentate. On another side, the formed GLYA was weakly adsorbed through two O atoms bridging/bonding to two Ti atoms. Due to the longer Ti–Ti distance in anatase, C–C cleavage of GLYA was obviously inhibited. The rutile support with shorter Ti–Ti distance inevitably led to obvious C–C cleavage. The discovery of the support effect could offer an alternative method to controllably regulate product distribution and offers specific perspective on designing efficient catalysts in semicontinuous oxidation reactions.

Sunlight-induced dehydrogenation rearrangement of the dititanium complex [Ti(η5-C5HMe4)(μ-η1: η5-C5Me4)

Sunlight photolysis of the triplet state (S = 1) dititanium compound 1 induced its rearrangement to diamagnetic 2, which was a molecule containing two hydrogens less. The cage structure of 2 was determined by single crystal X-ray diffraction and was corroborated fully by 1H and 13C NMR spectra that identified three simple bridging moieties — a hydrogen atom, a methine carbon and a methylene carbon. Its extremely short Ti−Ti distance 2.7537(7) Å causes a strong distortion of the bridging fulvalene ligand, which becomes η5- bonded to one Ti(IV) and connected by two σ-bonds from nearest carbon atoms of its other ring to the other Ti(IV) of 2. Other photolytical byproducts in very minor amounts were also isolated, which differed from 2 by the absence of one bridging moiety: compound 4 lacked the methine group and compound 5 had no bridging hydrogen. In the latter cases, the Ti−Ti distance fell in the range 3.2077(8) – 3.5543(12) Å and the fulvalene ligand was coordinated in the common µ-η5: η5-mode to both titanium atoms. The octamethylfulvalene ligands in 4 and 5 had their ring planes rotated mutually by about 40° in order to relieve the steric hindrance between their methyl groups. The thermally robust µ-oxo complex 3 obtained from reacting 2 with water showed a very similar structure.

Electronic structure and spin properties study on 2D h-BN nanosheet with Ti or Fe doping

The electronic structure and spin properties of Titanium (Ti) or Iron (Fe) doped hexagonal boron nitride (h-BN) nanosheet have been studied by using ab initio study based on density functional theory (DFT). GGA + U calculations show that one Ti or Fe atom can introduce local magnetic states into the system. Impurity levels will be generated in band gap, and this will lead to spin polarization. The calculated magnetic moments are 1.0 μB and 2.9 μB for Ti and Fe, respectively. Furthermore, the magnetic moments are all contributed by the d orbitals of doped atoms in h-BN monolayer. The studies of magnetic coupling reveal that two Ti atoms are mainly coupled antiferromagnetically at different distances between Ti atoms in h-BN monolayer. The Ti-doped system is coupled ferromagnetically only when Ti–Ti distance is 6.625 Å. While the magnetic coupling exhibits regular oscillation characteristics in the system with two Fe atoms doping at different distances. This novel property in Fe-doped h-BN nanosheet provides a new way to control the spin property of material. Our research is beneficial to the development of spintronics.

Amorphous and crystalline TiO2 nanoparticle negative electrodes for sodium-ion batteries

Titanium dioxide (TiO2) is a promising negative electrode for sodium ion batteries (SIBs). Although TiO2 materials with amorphous (A-TiO2) and single-phase crystalline structures (C–TiO2) have been separately explored, the study to compare the fundamental electrochemistry of A-TiO2 and C–TiO2 is limited. In this work, we investigated A-TiO2 and C–TiO2 nanoparticles with identical chemical composition and morphology. C–TiO2 exhibits enhanced electrochemical performance than A-TiO2 in terms of rate capability and cycle life. Cyclic voltammetry (CV) analysis suggests reversible Na ion insertion/extraction in C–TiO2. However, such process is irreversible in the case of A-TiO2. The charge storage mechanisms in both samples were studied to show that diffusion-controlled intercalation process becomes significant in C–TiO2 sample. The C–TiO2 sample has a better Na+ diffusivity measured through the galvanostatic intermittent titration technique (GITT) compared to A-TiO2, which corroborates well with the rate capability study. Furthermore, the evolution of local structure of the TiO2 samples was analyzed by ex situ pair distribution function (PDF) to understand the variation in electrochemical properties. It reveals that the corner-shared Ti–Ti distance along Na ion diffusion pathway increases with the increase of crystallinity, leading to the expanded diffusion channels and therefore more active sites and faster diffusion.

Quantitative analysis of local fine structure on diffusion of point defects in passive film on Ti

The diffusion of point defects in passivation determines all physico-electrochemical processes in materials corrosion and protection. In this study, a multiscale quantitative methodology was developed to reveal the diffusivity of oxygen vacancies on titanium surface (～5.0 nm thickness) in 1.0 M H2SO4 solution based on X-ray absorption fine structure (XAFS), combining with electrochemical impedance spectroscopy (EIS) and Mott-Schottky. EIS equivalent circuit exhibits that the high electronic field across passive film is 1.06 × 106 V cm–1. Mott-Schottky space charge capacitance indicates n-type semiconducting film with the donor density of ～1021 cm–3. Three important structure parameters have been firstly proposed from XAFS theoretical calculation at Ti K-edge to quantitatively describe the point defects transport between metal/film/solution interfaces. The half-jump distance equals half Ti–Ti distance subtly changing with oxidation potentials. The coordination coefficient is defined as the probability of activation jump from Ti–O coordination. And the Debye-Waller factor of structure disorder is related to the donor density of Mott-Schottky. Overall, the diffusivity of oxygen vacancies is in the range of (1.84–4.71) × 10–17 cm2 s–1 under the electric field, which determines the interfacial equilibrium of passivation and dissolution during potentiodynamic polarization. And the activation energy for motion has a minimum of 0.89 eV at 1.5 V. This multiscale quantitative methodology predicts well the potential dependent steady-state in the corrosive system.

Transfer of the triceps brachii to the finger and thumb extensors: Anatomical study and report on one case

Our aims were to study the anatomical feasibility of triceps brachii long head (TBLH) transfer to the extensor digitorum communis (EDC) and extensor pollicis longus (EPL) tendons through a medial route, and to report on its first clinical application. Dissections were conducted on 10 fresh-frozen cadaver specimens. Using a posteromedial approach, the TBLH was separated from the remaining triceps and extended distally with a fascia lata strip. This strip was then tunneled through a medial route and secured distally to the EDC and EPL tendons. The transfer tenodesis effect during elbow extension was assessed with metacarpophalangeal (MCP) joint motion of the thumb and index finger, and the distance between the thumb and index finger tips (TI distance). This transfer was performed in an eight-year-old boy with incomplete recovery of a right brachial plexus birth palsy; preoperatively, shoulder and elbow functions were recovered as well as active gripping distally, but he had no active wrist or finger extension. With the trapeziometacarpal and radiocarpal joints stabilized, 90° elbow extension provided a mean extension of the thumb and index finger MCP joints of 34 ± 5° and 90 ± 11°, respectively, with a mean TI distance of 116 ± 16 mm. Twelve months after surgery, the boy had full active MCP joint extension, independent from elbow extension. Transferring the TBLH to the EDC and EPL tendons is anatomically feasible. Larger clinical studies will be needed to assess more adequately its functional outcomes.

Binuclear pentalene titanium carbonyls involved in the deoxygenation of carbon dioxide

The complete series of binuclear pentalene titanium carbonyls Pn2Ti2(CO)n and Pn†2Ti2(CO)n (Pn = pentalene; Pn† = 1,4-(iPr3Si)2C8H4; n = 0, 1, 2, 3, 4), including Pn†2Ti2(CO)2 obtained experimentally from Pn†2Ti2 and carbon dioxide, have been investigated by density functional theory. For the carbonyl-free Pn2Ti2 system the singlet structure is found to lie 22.5 and 18.5 kcal/mol in energy below the isomeric triplet and quintet structures, respectively. However, for the experimentally known Pn†2Ti2 system (Pn† = 1,3-(iPr3Si)2C8H4) the singlet, triplet, and quintet spin state structures have essentially equal energies within 0.3 kcal/mol suggesting the possibility of complicated magnetic behavior. The Ti–Ti distance of 2.399 Å found in crystalline Pn†2Ti2 by X-ray crystallography is closest to the 2.415 Å Ti-Ti distance predicted for the triplet spin state structure. Carbonylation of Pn2Ti2 results in successive lengthening of the Ti-Ti distance as CO groups are added. Three CO groups are the maximum number that can be introduced into a viable Pn2Ti2(CO)n derivative as indicated by the predicted exothermic CO dissociation energy of the tetracarbonyl Pn2Ti2(CO)4. The lowest energy structure for the monocarbonyl Pn2†Ti2(CO) has a four-electron donor bridging η2-μ-CO group in accord with the experimental structure. The lowest energy structure for the dicarbonyl Pn†2Ti2(CO)2 has exclusively terminal CO groups in a cis configuration, again in accord with the experimental Pn†2Ti2(CO)2 structure. Two terminal CO groups are accompanied by a third highly unsymmetrical semibridging CO group in the lowest energy structures for the tricarbonyls Pn2Ti2(CO)3 and Pn†2Ti2(CO)3. However, the lowest energy structures for the tetracarbonyls Pn2Ti2(CO)4 and Pn†2Ti2(CO)4 have exclusively terminal CO groups.

Self-organizing systems in planetary physics: Harmonic resonances of planet and moon orbits

The geometric arrangement of planet and moon orbits into a regularly spaced pattern of distances is the result of a self-organizing system. The positive feedback mechanism that operates a self-organizing system is accomplished by harmonic orbit resonances, leading to long-term stable planet and moon orbits in solar or stellar systems. The distance pattern of planets was originally described by the empirical Titius–Bode law, and by a generalized version with a constant geometric progression factor (corresponding to logarithmic spacing). We find that the orbital periods Ti and planet distances Ri from the Sun are not consistent with logarithmic spacing, but rather follow the quantized scaling (Ri+1/Ri)=(Ti+1/Ti)2/3=(Hi+1/Hi)2/3, where the harmonic ratios are given by five dominant resonances, namely (Hi+1:Hi)=(3:2),(5:3),(2:1),(5:2),(3:1). We find that the orbital period ratios tend to follow the quantized harmonic ratios in increasing order. We apply this harmonic orbit resonance model to the planets and moons in our solar system, and to the exo-planets of 55 Cnc and HD 10180 planetary systems. The model allows us a prediction of missing planets in each planetary system, based on the quasi-regular self-organizing pattern of harmonic orbit resonance zones. We predict 7 (and 4) missing exo-planets around the star 55 Cnc (and HD 10180). The accuracy of the predicted planet and moon distances amounts to a few percents. All analyzed systems are found to have ≈ 10 resonant zones that can be occupied with planets (or moons) in long-term stable orbits.

Insights from arsenate adsorption on rutile (110): grazing-incidence X-ray absorption fine structure spectroscopy and DFT+U study.

Insights into the bonding of As(V) at the metal oxide/aqueous interface can further our understanding of its fate and transport in the environment. The motivation of this work is to explore the interfacial configuration of As(V) on single crystal rutile (110) using grazing-incidence X-ray absorption fine structure spectroscopy (GI-XAFS) and planewave density functional calculations with on-site repulsion (DFT+U). In contrast to the commonly considered corner-sharing bidentate binuclear structure, tetrahedral As(V) binds as an edge/corner-sharing tridentate binuclear complex on rutile (110), as evidenced by observation of three As-Ti distances at 2.83, 3.36, and 4.05 Å. In agreement with the GI-XAFS analysis, our DFT+U calculations for this configuration resulted in the lowest adsorption energy among five possible alternatives. In addition, the electron density difference further demonstrated the transfer of charge between surface Ti atoms and O atoms in AsO4. This charge transfer consequently induced the formation of a chemical bond, which is also confirmed by the partial density of states analysis. Our results may shed new light on coupling the GI-XAFS and DFT approaches to explore molecular-scale adsorption mechanisms on single crystal surfaces.

The electrochemical and local structural analysis of the mesoporous Li4Ti5O12 anode

Mesoporous lithium titanate microsphere anodes have been made by hydrothermal synthesis. Layered hydrous lithium titanate was obtained after hydrothermal reaction and Li4Ti5O12 microspheres assembled from nanosheets were subsequently formed by thermal treatment. This results in improved voltage profiles and charge/discharge dynamics. Mesoporous lithium titanate microspheres showed stable cycling performances, with high capacity retention (140 mAh g−1) even after 4000 cycles. In order to understand the functioning of this promising anode material at the molecular level, we used in-situ X-ray absorption spectroscopy (XAS). The XAS results verify the Ti conversion between Ti4+ and Ti3+ during charge/discharge cycling and demonstrate that this reduction is accompanied by small changes Ti–O distance but no detectable change in Ti–Ti distance. This anion re-arrangement suggests a structural explanation for the fact that this material is electrochemically very stable even under higher current density cycling.

First principles study of the electronic structure and magnetism of oxygen-deficient anatase TiO2 (0 0 1) surface

We have studied the electronic structure and magnetic properties of oxygen vacancy on anatase TiO2 (001) surface using density functional theory (DFT) calculations. We find that the oxygen vacancy on the surface may be responsible for the unexpected ferromagnetism in anatase TiO2 films without doping. The formation energies of surface vacancies are calculated. Results of our first-principles GGA+U calculations show that the oxygen vacancy at the ridge has the lowest formation energy. The spins induced by the local oxygen vacancy form a stable ferromagnetic state, and the anion vacancy can result in a magnetic moment of 1.63μB. The localized state of spin polarization will be formed in the band gap. The magnetic moment which is produced by the oxygen vacancy mainly comes from the d orbitals of two low-charge-state Ti ions converted from Ti4+ ions adjacent to the surface oxygen vacancy. We calculate the magnetic coupling between the two oxygen vacancies at the ridge in different distances. Although the spin dimerization will be formed along with the decrease of Ti–Ti distance, the results also show that the two oxygen vacancies on anatase TiO2 (001) surface are mainly coupled ferromagnetically. In addition, the other kind of oxygen vacancy at the valley can also induce the ferromagnetism on the surface. The experimentally observed d0-ferromagnetism behavior in TiO2 system is in good agreement with our calculated results.

Structural investigations in helium charged titanium films using grazing incidence XRD and EXAFS spectroscopy

The crystal structure and local atomic arrangements surrounding Ti atoms were determined for He-charged hexagonal close-packed (hcp) Ti films and measured at glancing angles by synchrotron radiation X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) spectroscopy, respectively. The charged specimens were prepared by direct current magnetron sputtering with a He/Ar mixture. He atoms with a relatively medium concentration (He/Ti atomic ratio as high as 17at.%) were incorporated evenly in the deposited films. XRD results showed the changes in the peak intensities in Ti films with different He contents. EXAFS Fourier Transform analysis indicated that the average Ti–Ti distance decreased significantly, and proved the existence of phase transition.

EXAFS and DFT studies of microscopic structure with different density upon Zn(II) adsorption on anatase TiO2

Microscopic structures of Zn(II) adsorbed on anatase TiO2 surface with different densities were studied using extended X-ray absorption fine structure (EXAFS) spectroscopy and density functional theory (DFT) calculation. Quantitative analysis of the EXAFS spectra showed that microscopic structures of Zn(II) were fourfold coordinated complexes, and different microscopic structures were present of the solid surface. Three modes of corner–corner/sharing-corner/sharing-edge adsorptions on anatase (101) face cluster were calculated by the DFT method. The results from DFT method were consistent with the EXAFS fittings. The optimized Zn–O average distance of the Zn–O tetrahedron was determined as about 2.00 A. The Zn–Ti distance was 3.69 A for the corner–corner adsorption, 3.35 A for the sharing-corner adsorption, and 3.02 A for the sharing-edge adsorption. According to the adsorption energies calculated by the DFT method, the microscopic structure of corner–corner adsorption was less stable than those of the other adsorption modes. With the increasing adsorption density, the corner–corner adsorption mode would be enhanced more intensively than the other adsorption modes.

Anion packing, hole filling, and HF solvation in A2(HF)nB12F12 and K2(HF)TiF6 (A = K, Cs)

The crystal structures of three new HF solvates of fluoroanion salts of alkali metal ions are reported, K2(HF)TiF6, K2(HF)3B12F12, and Cs2(HF)B12F12. The anion packing in K2(HF)TiF6 (P21/m) is distorted cubic close-packed with Ti⋯Ti distances that range from 5.717(1) to 7.394(1)Å (average 6.18Å). Half of the K+ ions are in Td holes and half are in Oh holes (i.e., this is a distorted version of the Cs2S structure). Each HF molecule is bonded to a K+ ion in the Oh holes (KF(H)=2.679(5)Å) and also weakly interacts with two other K+ ions in adjacent Oh holes (K⋯F(H)=3.238(2)Å). The anion packing in K2(HF)3B12F12 (Fm3¯m) is simple cubic. The (B12 centroid)⋯(B12 centroid) distance (⊙⋯⊙ distance) is 7.242Å, and disordered K2(μ-HF)32+ cations occupy each cube. The anion packing in Cs2(HF)B12F12 (P21/c) is distorted hexagonal close-packed with ⊙⋯⊙ distances that range from 7.217 to 9.408Å (average 8.304Å). The HF molecule bridges Cs+ ions in adjacent Oh holes, forming infinite Cs+(μ-HF)Cs+(μ-HF) chains. The other half of the Cs+ ions are in Td holes, displaced nearly 1Å from the center of those holes. This structure is similar to the distorted Ni2In structure exhibited by Cs2(H2O)B12F12. The new results are used to compare and contrast the strength of M–F(H) interactions with M–F interactions involving F atoms from fluoroanions as well as the solid-state packing of icosahedral B12F122− anions and octahedral MF62− anions in alkali-metal salts, both with and without the inclusion of weakly-basic HF solvent molecules.

High surface area ordered mesoporous nano-titania by a rapid surfactant-free approach

Immersion of solid nanorods of the commercial metal–organic precursor [Ti(OCH3)4]4 into boiling water results in their rapid topotactic transformation into rod-shaped colloid crystals built up of uniform crystalline anatase nanoparticles with average particle diameter 5.0 ± 1 nm forming rather regular wormhole-type mesoporosity with average pore diameter 4.1 nm and a record-high surface area and mesopore volume of 288 m2 g−1 and 0.42 cm3 g−1 respectively. This structure emerges through reorganization of the intermediate ordered mesoporous lamellar structure. The distance between lamellae is about 3 nm. They are oriented parallel to the {1 0 0} crystallographic direction in the precursor crystals and originate most probably through contraction and densification of the layers of precursor molecules in the course of the process. Similar mechanisms are observed even for hydrolytic transformation of nanocrystals of other alkoxide precursors, derivatives of volatile alcohols, permitting to achieve surface area up to 350 m2 g−1. The obtained material is completely free from organics, but highly hygroscopic. Powders produced within 3 min show very broad X-ray diffraction peaks, indicating low volume coherence domains, but continued refluxing offers a strongly improved XPD pattern after 10 min and a fully crystalline material with coherence domain equivalent to the individual particle size after only 30 min. The latter material exhibits well defined Ti–Ti distances in the structure typical for a crystalline anatase phase according to EXAFS spectroscopy. It displays strong photochemical activity in destruction of methylene blue dye. When an aqueous dispersion of superparamagnetic Fe3O4 nanoparticles is applied for hydrolysis the product is a magnetic nanocomposite, easily and rapidly removable from solution by a magnet. The produced fully crystalline porous TiO2 possesses attractive characteristics as an adsorbent for water remediation tested through adsorption of dichromate anions.

Temperature-dependent neutron diffraction on TiI3

Abstract Crystal structures of TiI3 were determined and refined at selected temperatures between 4 and 340 K against neutron powder diffraction data. On heating, thermal expansion is found to increase abruptly at the phase transition at T c = 323 K. Most prominently, linear thermal expansion is highly anisotropic and small along c (i.e. along chains of Ti atoms) in the low-temperature phase, while above T c it is much larger along c. An order parameter is defined by the ratio between the long and the short Ti—Ti distances on the metal chains. The temperature dependence of the order parameter indicates the transition to be of first order.

Synthesis and structure of dinuclear dimethylene- or 1,4-phenylene-linked bis(decamethyltitanoceneoxide) (Ti III) complexes

The singly tucked-in titanocene [Ti(η 5-C 5Me 5)(η 5:η 1-C 5Me 4CH 2)] ( 1) reacts smoothly with ethylene glycol or hydroquinone to give bis(titanoceneoxide) (Ti III) complexes [CH 2OTi(η 5-C 5Me 5) 2] 2 ( 2) and [(η 5-C 5Me 5) 2TiOC 6H 4OTi(η 5-C 5Me 5) 2] ( 3) containing dimethylene and 1,4-phenylene link, respectively. EPR spectra of 2 in 2-methyltetrahydrofuran glass and 3 in toluene glass revealed that the unpaired d 1 electrons are in interaction to form triplet state molecules. The Ti–Ti distance derived from the zero-field splittings D for the two conformations of 2 (7.42 Å and 7.66 Å) are in good agreement with the Ti–Ti distance of 7.2430(7) Å from the X-ray diffraction single-crystal analysis. For 3, however, the Ti–Ti distance derived from D (7.65 Å) is by 1.47 Å shorter than the crystallographic distance of 9.1230(8) Å that indicates an enhancement of the through-space dipole–dipole interaction due to the presence of a conjugated quinonide link.

Density functional studies of the adsorption for hydrated Zn(II) ion on anatase TiO 2 (1 0 1) surface

Density functional theory (DFT) calculations were performed to investigate surface complex structures and reaction energies of hydrated Zn(II) adsorption on anatase TiO 2 (1 0 1) surface. Six types of microstructure clusters were employed, including single-corner sharing (SC), corner sharing (TC), two types of double-corner sharing (DC1 and DC2) and two types of single-edge sharing (SE1 and SE2). Results showed that the Zn–O distances in the six microstructures were all around 2.00 Å, equivalent to those determined by EXAFS spectroscopy, and the Zn–Ti distances ranged from 3.00 to 3.80 Å. The Zn–Ti distance in SE mode was the shortest, whereas that in SC mode was the longest. The reaction energies absolute value for the six modes were in the order of DC1 > DC2 > SC ≈ SE1 > TC > SE2. It could be conferred that both the double-corner sharing modes were relatively more stable than the others.

Adsorption of Xe atoms on the TiO2(110) surface: A density functional study

The interaction of xenon atoms with the TiO2(1 1 0) surface of rutile has been studied by density functional theory methods. Five different possible adsorption sites on the relaxed and clean TiO2(1 1 0) surface and on two different type of oxygen vacancies possible on this oxide substrate have been considered. In the case of the defect-free substrate, and when compared with a previous study concerning the adsorption of Ar atoms also on TiO2(1 1 0), the xenon atom, as a larger and easier polarizable species, is shown to have a deeper physisorption well, as expected. Likewise, Xe atoms prefer to be bounded to positions nearby the outermost titanium atoms as found previously for Ar. This is in agreement with most studies concerning rare gases adsorbed on transition metal surfaces. In the case of the reduced surfaces, it is found that the interaction is more favourable in the protruding rows. The interaction is dominated by dispersion forces and DFT + dispersion energies are 3.5–5 times larger than the non-corrected DFT values and Xe-surface distances are smaller. Finally, an interesting correlation is obtained for the calculated interaction energies and the Xe–Ti distance.