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Title: Formaldehyde adsorption and decomposition on rutile (110): A first-principles study

Authors:
;
Publication Date:
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1397339
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Surface Science
Additional Journal Information:
Journal Volume: 652; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-10-04 21:07:32; Journal ID: ISSN 0039-6028
Publisher:
Elsevier
Country of Publication:
Netherlands
Language:
English

Citation Formats

Liu, Liming, and Zhao, Jin. Formaldehyde adsorption and decomposition on rutile (110): A first-principles study. Netherlands: N. p., 2016. Web. doi:10.1016/j.susc.2015.12.036.
Liu, Liming, & Zhao, Jin. Formaldehyde adsorption and decomposition on rutile (110): A first-principles study. Netherlands. doi:10.1016/j.susc.2015.12.036.
Liu, Liming, and Zhao, Jin. 2016. "Formaldehyde adsorption and decomposition on rutile (110): A first-principles study". Netherlands. doi:10.1016/j.susc.2015.12.036.
@article{osti_1397339,
title = {Formaldehyde adsorption and decomposition on rutile (110): A first-principles study},
author = {Liu, Liming and Zhao, Jin},
abstractNote = {},
doi = {10.1016/j.susc.2015.12.036},
journal = {Surface Science},
number = C,
volume = 652,
place = {Netherlands},
year = 2016,
month =
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.susc.2015.12.036

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  • The adsorption and dissociation of H{sub 2}S on MgO(100), Ni-doped MgO(100), and ZnO(0001) was studied using first-principles density-functional calculations (DFT-GGA) and periodic supercells. The bonding of H{sub 2}S and its S-containing dissociated species (HS and S) is substantially stronger on ZnO(0001) than on MgO(100), making dissociation easier on zinc oxide. This behavior can be explained by the smaller ionicity in ZnO, which leads to a larger electron density around the Zn atoms and a larger reactivity toward S-containing molecules. Replacing some of the metal centers of MgO(100) with Ni atoms enhances the binding of S-containing species through new electronic statesmore » associated with the Ni 3d levels and located above the occupied {l_brace}O 2p + Mg 3s{r_brace} bands. In addition, structural defects, like steps, expose metal centers with lower coordination and larger reactivity than pentacoordinated Mg atoms in MgO(100). A simple model based on perturbation theory and band-orbital mixing is able to explain the differences in the reactivity of MgO(100) and ZnO(0001) and the behavior of other oxides (Al{sub 2}O{sub 3}, Cr{sub 2}O{sub 3}, Cr{sub 3}O{sub 4}, Cu{sub 2}O) in the presence of sulfur-containing molecules. The model predicts a negative correlation between the reactivity of the oxides and the size of the electronic band gap, with the chemical activity of an oxide depending mainly on how well its bands mix with the orbitals of H{sub 2}S. The electrostatic interactions between the Madelung field of the oxide and the dipole moment of the molecule play only a secondary role in bonding.« less
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  • We model rutile titanium dioxide nanocrystals (NCs) up to ~1.5 nm in size to study the effects of quantum confinement on their electronic and optical properties. Ionization potentials (IPs) and electron affinities (EAs) are obtained via the perturbative GW approximation (G 0W 0) and ΔSCF method for NCs up to 24 and 64 TiO 2 formula units, respectively. These demanding GW computations are made feasible by using a real-space framework that exploits quantum confinement to reduce the number of empty states needed in GW summations. Time-dependent density functional theory (TDDFT) is used to predict the optical properties of NCs upmore » to 64 TiO 2 units. For a NC containing only 2 TiO 2 units, the offsets of the IP and the EA from the corresponding bulk limits are of similar magnitude. However, as NC size increases, the EA is found to converge more slowly to the bulk limit than the IP. The EA values computed at the G 0W 0 and ΔSCF levels of theory are found to agree fairly well with each other, while the IPs computed with ΔSCF are consistently smaller than those computed with G 0W 0 by a roughly constant amount. TDDFT optical gaps exhibit weaker size dependence than GW quasiparticle gaps, and result in exciton binding energies on the order of eV. Finally, altering the dimensions of a fixed-size NC can change electronic and optical excitations up to several tenths of an eV. The largest NCs modeled are still quantum confined and do not yet have quasiparticle levels or optical gaps at bulk values. Nevertheless, we find that classical Mie-Gans theory can quite accurately reproduce the line shape of TDDFT absorption spectra, even for (anisotropic) TiO 2 NCs of subnanometer size.« less
  • We model rutile titanium dioxide nanocrystals (NCs) up to ~1.5 nm in size to study the effects of quantum confinement on their electronic and optical properties. Ionization potentials (IPs) and electron affinities (EAs) are obtained via the perturbative GW approximation (G 0W 0) and ΔSCF method for NCs up to 24 and 64 TiO 2 formula units, respectively. These demanding GW computations are made feasible by using a real-space framework that exploits quantum confinement to reduce the number of empty states needed in GW summations. Time-dependent density functional theory (TDDFT) is used to predict the optical properties of NCs upmore » to 64 TiO 2 units. For a NC containing only 2 TiO 2 units, the offsets of the IP and the EA from the corresponding bulk limits are of similar magnitude. However, as NC size increases, the EA is found to converge more slowly to the bulk limit than the IP. The EA values computed at the G 0W 0 and ΔSCF levels of theory are found to agree fairly well with each other, while the IPs computed with ΔSCF are consistently smaller than those computed with G 0W 0 by a roughly constant amount. TDDFT optical gaps exhibit weaker size dependence than GW quasiparticle gaps, and result in exciton binding energies on the order of eV. Finally, altering the dimensions of a fixed-size NC can change electronic and optical excitations up to several tenths of an eV. The largest NCs modeled are still quantum confined and do not yet have quasiparticle levels or optical gaps at bulk values. Nevertheless, we find that classical Mie-Gans theory can quite accurately reproduce the line shape of TDDFT absorption spectra, even for (anisotropic) TiO 2 NCs of subnanometer size.« less
  • Based on first-principles electronic structure calculations we find that the bridging oxygen vacancies on the (1 1 0) surface is more favorable and may be responsible for the unexpected ferromagnetism in undoped rutile TiO{sub 2}. Our results show that the ferromagnetism largely originates from the d orbitals of low-charge-state Ti ions converted from Ti{sup 4+} ions induced by the surface oxygen vacancies. The second-nearest neighbors of these ions (fivefold coordinated Ti) also contribute to the total magnetic moments. The spins induced by the local oxygen vacancies form a ferromagnetic arrangement. -- Graphical Abstract: The study investigates the magnetic properties ofmore » the oxygen-deficient rutile TiO{sub 2}(1 1 0) surface from first principle calculations. The adjacent oxygen vacancies form a ferromagnetic arrangement due to the double exchange interaction. Display Omitted Highlights: {yields} There should be more V{sub O}'s than V{sub Ti}'s on the (1 1 0) surface layer of TiO{sub 2}. {yields} Magnetic moments induced by the isolated V{sub O} form a paramagnetic arrangement. {yields} Magnetic moments induced by the concentrated V{sub O}'s form a ferromagnetic arrangement. {yields} Double exchange is the dominant coupling mechanism of the ferromagnetism.« less