Atomic-scale structure of amorphous TiO2 by electron, X-ray diffraction and reverse Monte Carlo simulations

Petkov, Valeri; Holzhüter, G.; Tröge, U; Gerber, Th.; Himmel, B.

doi:10.1016/s0022-3093(98)00418-9

Cited by 126 publications

(176 citation statements)

References 31 publications

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“…This fact is also manifest in the asymmetry of the first peak in the t TiTi (r), which, in the amorphous phase at room temperature, is resolved into two separate Ti-Ti peaks in our model. Such splitting of the Ti-Ti peak has been observed previously [20,45,58] in amorphous TiO 2 . …”

Section: Local Structure Of Liquid Tiosupporting

confidence: 80%

“…TiO 2 is often used as a component in melt-derived mixed oxide glasses to increase refractive index [14], or as a nucleating agent in glass-ceramics [15,16]. [19]) polyhedra, while in amorphous TiO 2 , Ti is found to have an average coordination number laying between five and six [20] (dependent upon growth method). TiO 2 is strongly polymorphic, with at least five forms known to be metastable with respect to Rutile under ambient conditions ( Fig.…”

Section: Introductionmentioning

confidence: 99%

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Structure of molten titanium dioxide

et al. 2014

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The x-ray structure factor of molten TiO 2 has been measured for the first time, enabled by the use of aerodynamic levitation and laser beam heating, to a temperature of T = 2250(30) K. Ti-O coordination number in the melt is close to n TiO = 5.0(2), with modal Ti-O bond length r TiO = 1.881(5) Å, both values being significantly smaller than for the high temperature stable Rutile crystal structure (n TiO = 6.0, r TiO = 1.959 Å). The structural differences between melt and crystal are qualitatively similar to those for alumina, which is rationalized in terms of the similar field strengths of Ti 4+ and Al 3+. The diffraction data are used to generate physically and chemically reasonable structural models, which are then compared to the predictions based on various classical molecular dynamics (MD) potentials. New interatomic potentials, suitable for modelling molten TiO 2 , are introduced, given the inability of existing MD models to reproduce the diffraction data. These new potentials have the additional great advantage of being able to predict the density and thermal expansion of the melt, as well as solid amorphous TiO 2 , in agreement with published results. This is of critical importance given the strong correlation between density and structural parameters such as n TiO . The large thermal expansion of the melt is associated with weakly temperature dependent structural changes, whereby simulations show that n TiO = 5.85(2) -(3.0(1) x 10 -4 )T (K, 2.75 Å cut-off). The TiO 2 liquid is structurally analogous to the geophysically relevant high pressure liquid silica system at around 27 GPa. We argue that the predominance of 5-fold polyhedra in the melt implies the existence of as yet undiscovered TiO 2 polymorphs, based on lowerthan-octahedral coordination numbers, which are likely to be metastable under ambient conditions. Given the industrial importance of titanium oxides, experimental and computational searches for such polymorphs are well warranted.

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Section: Local Structure Of Liquid Tiosupporting

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Structure of molten titanium dioxide

et al. 2014

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“…Fig. 1, the calculated PRDFs agree reasonably well with the experimental data for sputtered TiO 2 amorphous layers in [10] in terms of the form, heights and position of peaks. Splitting of the first peak in PRDF for the Ti-Ti pair is also found in our model like that observed in experiment that the prepeak is centered at around 3.00 Å and the main peak is at 3.47 Å versus 3.00 Å and 3.55 Å obtained in experiment, respectively (see Table 2).…”

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confidence: 78%

“…Concerning on the amorphous TiO 2 it was found a few works in literature. Atomic structural quantities of amorphous TiO 2 such as PRDFs, interatomic distances and coordination numbers have been studied by electron, X-ray diffraction and reverse Monte-Carlo simulation [10]. The atomic arrangement in amorphous TiO 2 has been found to resemble that occurred in brookite and described well as an assembly of short staggered chains of Ti-O octahedra [10].…”

Section: Introductionmentioning

confidence: 99%

Structural properties of simulated liquid and amorphous TiO₂

Hoang

2007

Physica Status Solidi (b)

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Structural properties of liquid and amorphous TiO 2 have been studied in a model containing 3000 particles under periodic boundary conditions with the pairwise interatomic potentials proposed by Matsui and Akaogi. Models have been obtained by cooling from the melt via molecular dynamics (MD) simulation. Structural properties of an amorphous model obtained at 350 K have been analyzed in details through the partial radial distribution functions (PRDFs), coordination number distributions, bond-angle distributions and interatomic distances. Calculations show that calculated data agree well with the experimental ones. The evolution of structure upon cooling from the melt was observed and discussed. Calculations show that amorphous TiO 2 has a distorted octahedral network structure with the mean coordination number

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“…37,38,39,40 The distance between the support atoms (see Figure 1) was taken from radial distribution functions obtained from XRD, NS, and EXAFS measurements. 41,42,43 Density functional theory calculations were performed using the B3LYP functional. 44,45,46 The 6-31 g basis set was used for all atoms except Ti, V, and Zr.…”

Section: Theoretical Methodsmentioning

confidence: 99%

A Density Functional Theory Study of the Oxidation of Methanol to Formaldehyde over Vanadia Supported on Silica, Titania, and Zirconia

2002

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Density functional theory was used to investigate the mechanism and kinetics of methanol oxidation to formaldehyde over vanadia supported on silica, titania, and zirconia. The catalytically active site was modeled as an isolated VO 4 unit attached to the support. The calculated geometry and vibrational frequencies of the active site are in good agreement with experimental measurements both for model compounds and oxidesupported vanadia. Methanol adsorption is found to occur preferentially with the rupture of a V-O-M bond (M = Si, Ti, Zr) and with preferential attachment of a methoxy group to V. The vibrational frequencies of the methoxy group are in good agreement with those observed experimentally as are the calculated isobars. The formation of formaldehyde is assumed to occur via the transfer of an H atom of a methoxy group to the O atom of the V=O group. The activation energy for this process is found to be in the range of 199-214 kJ/mol and apparent activation energies for the overall oxidation of methanol to formaldehyde are predicted to lie in the range of 112-123 kJ/mol, which is significantly higher than that found experimentally. Moreover, the predicted turnover frequency (TOF) for methanol oxidation is found to be essentially independent of support composition, whereas experiments show that the TOF is 10 3 greater for titania-and zirconia-supported vanadia than for silica-supported vanadia. Based on these findings, it is proposed that the formation of formaldehyde from methoxy groups may require pairs of adjacent VO 4 groups or V 2 O 7 dimer structures.3

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Atomic-scale structure of amorphous TiO2 by electron, X-ray diffraction and reverse Monte Carlo simulations

Cited by 126 publications

References 31 publications

Structure of molten titanium dioxide

Structure of molten titanium dioxide

Structural properties of simulated liquid and amorphous TiO₂

A Density Functional Theory Study of the Oxidation of Methanol to Formaldehyde over Vanadia Supported on Silica, Titania, and Zirconia

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Atomic-scale structure of amorphous TiO2 by electron, X-ray diffraction and reverse Monte Carlo simulations

Cited by 126 publications

References 31 publications

Structure of molten titanium dioxide

Structure of molten titanium dioxide

Structural properties of simulated liquid and amorphous TiO2

A Density Functional Theory Study of the Oxidation of Methanol to Formaldehyde over Vanadia Supported on Silica, Titania, and Zirconia

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Product

Resources

About

Structural properties of simulated liquid and amorphous TiO₂