Optical Properties and Band Structure of Titanium Carbide

Lye, R. G.; Logothetis, E. M.

doi:10.1103/physrev.147.622

Cited by 163 publications

(26 citation statements)

References 29 publications

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“…The optical properties of such nanocrystals have so far not been determined in the laboratory. The optical properties of TiC in the bulk have been studied extensively (Lye & Logothetis 1966;Alward et al 1975;Ihara et al 1975;Lynch et al 1980;Pflüger et al 1984;Koide et al 1990Koide et al , 1993Delin et al 1996;Espinosa-Magaña et al 2002). Although these studies are focused on the high energy range (the longest wavelength presented is 12 µm), they consistently find a large free electron contribution to the optical properties in the infrared.…”

Section: Titanium Carbide Nano-crystalsmentioning

confidence: 99%

The circumstellar envelope of the C-rich post-AGB star HD 56126

Hony

Tielens

Waters

et al. 2003

A&A

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Abstract. We present a detailed study of the circumstellar envelope of the post-asymptotic giant branch "21 µm object" HD 56126. We build a detailed dust radiative transfer model of the circumstellar envelope in order to derive the dust composition and mass, and the mass-loss history of the star. To model the emission of the dust we use amorphous carbon, hydrogenated amorphous carbon, magnesium sulfide and titanium carbide. We present a detailed parametrisation of the optical properties of hydrogenated amorphous carbon as a function of H/C content. The mid-infrared imaging and spectroscopy is best reproduced by a single dust shell from 1.2 to 2.6 radius around the central star. This shell originates from a short period during which the mass-loss rate exceeded 10 −4 M /yr. We find that the strength of the "21" µm feature poses a problem for the TiC identification. The low abundance of Ti requires very high absorption cross-sections in the ultraviolet and visible wavelength range to explain the strength of the feature. Other nano-crystalline metal carbides should be considered as well. We find that hydrogenated amorphous carbon in radiative equilibrium with the local radiation field does not reach a high enough temperature to explain the strength of the 3.3-3.4 and 6-9 µm hydrocarbon features relative to the 11-17 µm hydrocarbon features. We propose that the carriers of these hydrocarbon features are not in radiative equilibrium but are transiently heated to high temperature. We find that 2 per cent of the dust mass is required to explain the strength of the "30" µm feature, which fits well within the measured atmospheric abundance of Mg and S. This further strengthens the MgS identification of the "30" µm feature.Key words. stars: individual: HD 56126 -stars: AGB and post-AGB -stars: carbon -circumstellar matterstars: mass-loss -infrared: stars IntroductionPost-asymptotic giant branch stars (post-AGBs) are objects in which the strong AGB mass-loss has ceased while the remaining star is not (yet) hot enough to ionise the surrounding material. These objects are characterised by a double-peaked spectral energy distribution (SED). In the ultraviolet (UV) and visible range the central star is visible. In the mid-infrared (IR) range the light is dominated by emission from the dusty circumstellar envelope (CSE). Post-AGB stars are the prime objects to study stellar evolution near the very end of the AGB because they are the most recent evolutionary descendants of the AGB stars. Mass loss near the tip of the AGB is not well understood. There are indications that the mass-loss rates near the end of the AGB exceed the values predicted by Send offprint requests to: S. Hony, e-mail: shony@rssd.esa.int Based on observations taken at the European Southern Observatory, La Silla, Chile and observation obtained with ISO, an ESA project with instruments funded by ESA Member states (especially the PI countries: France, Germany, The Netherlands and the UK) with the participation of ISAS and NASA. the existing dust driven wind models...

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Section: Titanium Carbide Nano-crystalsmentioning

confidence: 99%

The circumstellar envelope of the C-rich post-AGB star HD 56126

Hony

Tielens

Waters

et al. 2003

A&A

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“…These similarities have suggested that the principal components of the bonding in the refractory hardmetals are related more closely to the metal-metal interactions of the transition metals than to the metal-nonmetal interactions of the common transition metal compounds (Kiessling 1957, Robins 1958. Support for this assumption has been provided by Lye and Logothetis (1966); who employed measurements of the optical reflectivity in conjunction with the LCAO formalism of Slater and Koster (1954) to calculate an electronic energy band structure for TiC• The result exhibited a close resemblance to the electronic structure of fcc transition metals (Lye 1967), and indied that electrons were transferred from the 2p states of the carbon atom to crystalline energy bands derived from the 3d states of the metal atom, as had been suggested earlier by Umanskii (1.943). This transfer of electrons between states of different symmetries compensates only partially for the negative charge deposited within the carbon atom spheres by the overlap of electronic wave functions associated with t.ie metal atoms.…”

Section: §1 Mroductionmentioning

confidence: 93%

Low temperature specific heat of vanadium carbide

Lowndes

Finegold

Lye

1970

The Philosophical Magazine: A Journal of Theoretical Experiment

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“…This fact is supported by many of electronic band structure calculathe reverse transfer (9). Recently, the Hartree-Fock-Slater (HFS) molecular orbital theories such as the Xascattered wave (SW) method of Johnson et al (13) (14) and the discrete variational (DVof Ellis et al (15) (16) have been successfully applied to study the electronic structure of metal clusters (17) and chemisorp-…”

Section: Introductionmentioning

confidence: 92%

Molecular Cluster Approach to the Electronic Structure and the Bonding Mechanism for Impurity Carbon Atom in Titanium Metal and for Titanium Monocarbide

1977

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Theoretical studies of the localized electronic structure and the bonding mechanism around impurity carbon atoms in titanium metal and for titanium monocarbide are made using the HartreeFock-Slater molecular cluster model. Orbital energies and results of Mulliken's population analysis are presented for Ti18, Ti18C and Ti14C1, clusters. Density-of-states curves for the Ti14C13 cluster are in good agreement with the photoelectron and soft X-ray spectra. Overlap populations are used to discuss the covalent bonding in these clusters. The effect of self-consistency for Ti14C13 cluster is also investigated.

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Optical Properties and Band Structure of Titanium Carbide

Cited by 163 publications

References 29 publications

The circumstellar envelope of the C-rich post-AGB star HD 56126

The circumstellar envelope of the C-rich post-AGB star HD 56126

Low temperature specific heat of vanadium carbide

Molecular Cluster Approach to the Electronic Structure and the Bonding Mechanism for Impurity Carbon Atom in Titanium Metal and for Titanium Monocarbide

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