Structural, elastic, vibrational and electronic properties of amorphous Sm2O3 from Ab Initio calculations

Olsson, Emilia; Cai, Qiong; Cottom, Jonathon; Jakobsen, Rasmus; Shluger, Alexander L.

doi:10.1016/j.commatsci.2019.109119

Cited by 15 publications

(9 citation statements)

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“…Following the success in experimental preparation of metastable metal alloys [67], theoretical models of oxide glasses are also usually obtained using a melt-quench procedure and molecular dynamics (MD) [68]. This technique has been used to model structures of amorphous a-HfO 2 , a-SiO 2 , a-Al 2 O 3 , a-ZnO, and a-Sm 2 O 3 [47,50,56,[69][70][71] as well as other non-glass-forming oxides [72]. Similarly, classical force-fields, [39,73-80] density-functional-based tight-binding [81] and DFT [41][42][43]64] simulations have been used to create models of a-TiO 2 structures.…”

Section: Computational Detailsmentioning

confidence: 99%

Disorder-induced electron and hole trapping in amorphous TiO2

2020

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Thin films of amorphous (a)-TiO 2 are ubiquitous as photocatalysts, protective coatings, photo-anodes, and in memory applications, where they are exposed to excess electrons and holes. We investigate trapping of excess electrons and holes in the bulk of pure amorphous titanium dioxide, a-TiO 2 , using hybrid density-functional theory (h-DFT) calculations. Fifty 270-atom a-TiO 2 structures were produced using classical molecular dynamics and their geometries fully optimized using h-DFT simulations. They have the density, distribution of atomic coordination numbers, and radial pair-distribution functions in agreement with experiments. The calculated average a-TiO 2 band gap is 3.25 eV with no states splitting into the band gap. Trapping of excess electrons and holes in a-TiO 2 is predicted at precursor sites, such as elongated Ti-O bonds. Single electron and hole polarons have average trapping energies (E T) of −0.4 eV and −0.8 eV, respectively. We also identify several types of electron and hole bipolaron states and discuss their stability. These results can be used for understanding the mechanisms of photo-catalysis and improving the performance of electronic devices employing a-TiO 2 films.

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Section: Computational Detailsmentioning

confidence: 99%

Disorder-induced electron and hole trapping in amorphous TiO2

2020

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“…The approach adopted is to run an ensemble of simulations using classical MD and a full melt-quench trajectory, followed by relaxation with a hybrid functional (sometimes preceded by a relaxation with a non-hybrid functional) to give accurate electronic properties. This has been successfully applied to amorphous normalSiO2 [32], normalTiO2, ZnO [33], normalSm2normalO3 [34], normalAl2normalO3 [35] and normalHfO2 [36,37], to compute e.g. defect formation energies, and activation energies for diffusion.…”

Section: Applicationsmentioning

confidence: 99%

Review: understanding the properties of amorphous materials with high-performance computing methods

Christie

2023

Phil. Trans. R. Soc. A.

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Amorphous materials have no long-range order in their atomic structure. This makes much of the formalism for the study of crystalline materials irrelevant, and so elucidating their structure and properties is challenging. The use of computational methods is a powerful complement to experimental studies, and in this paper we review the use of high-performance computing methods in the simulation of amorphous materials. Five case studies are presented to showcase the wide range of materials and computational methods available to practitioners in this field. This article is part of a discussion meeting issue ‘Supercomputing simulations of advanced materials’.

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“…[82] For example, the band structure of lanthanide oxides reveals that the 4f orbitals form subbands in the valence region, allowing overlap with the oxygen p-band, demonstrating the ability to engineer the electronic structure of 4f elements by combination with lighter elements for bond activation. [83] As a result of the ability of the 4f orbitals to polarize the 5d orbitals and, thus, enhance the interactions with the 3d orbitals, the coupling of 4f electrons with the s and d conduction electrons results in the optimized geometric and electronic structure of RE-based materials. In particular, the 4f electrons are delocalized into a 4f band and can undergo orbitally selective Mott transitions, [84,85] especially in RE SACs.…”

Section: Theoretical Advantages Of Re Sacsmentioning

confidence: 99%

Rare‐Earth Single‐Atom Catalysts: A New Frontier in Photo/Electrocatalysis

Wang

Zhu

et al. 2022

Small Methods

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through three steps: 1) at the catalyst surface, the reactants diffuse toward the active sites; 2) the reactants are adsorbed at the active sites and transformed into products via consecutive elementary reaction steps; 3) the products diffuse from the surface via chemical desorption. [4][5][6] To facilitate this transformational process, the catalytically active surface should contain many highly catalytically active sites. [7][8][9][10] However, in conventional bulk catalysts, typically, only a few surface atoms provide catalytic activity, and most of the subsurface atoms cannot directly participate in the reactions, thus resulting in atomic waste. [11][12][13][14][15] Recently, more efficient catalysts have been prepared by changing the active sites from those of a bulk catalyst to isolated atoms; these systems are known as single-atom catalysts (SACs). Thus, the term SAC is given to materials whose catalytically active sites are single atoms. The first discussion of SACs can be traced back to 2011, Zhang et al. reported Pt atoms anchored on FeO x (Pt 1 /FeO x ) for CO oxidation. [16] Crucially, when the size of catalysts reaches the atomic scale, distinctive properties that affect their chemical activities, conversion efficiencies, and stabilities emerge. In particular, unlike bulk catalysts, SACs maximize the use of the catalytically active metal atoms (nearly 100% atom efficiency). [17][18][19][20] Further, compared with bulk catalysts, SACs have unique advantages: 1) an unsaturated coordination environment that affects the affinity of the catalyst for intermediate species; 2) distinctive quantum size effects that yield discrete energy levels and frontier molecular orbital (FMO) occupancies; 3) strong atom support interactions that facilitate surface charge redistribution; 4) appropriate polarity to restrain shuttle effects during catalytic processes; 5) breaking of the energy scaling relationship based on the Sabatier principle for enhanced catalytic activity; and 6) site-to-site interactions between single atoms that enhance the catalytic kinetics. [21][22][23][24][25][26][27][28] In recent years, the use of transition-metal-based SACs [29][30][31] and precious-metal-based SACs [32][33][34] has developed rapidly, especially in the field of energy catalysis. In particular, research has focused on Fe, [35][36][37] Co, [38,39] Ni, [40,41] Mn, [42] Pt, [43,44] Ir, [45][46][47] Pd. [48,49] Owing to the strong atom-support interactions, the coupling of the metal and ligand orbitals in the support can result in changes in the d-band center (ε d ) of the metal atoms, [50,51] and this spin-orbit coupling, which results in a range of electronic states, is key to the success of heterogeneous Single-atom catalysts (SACs) provide well-defined active sites with 100% atom utilization, and can be prepared using a wide range of support materials. Therefore, they are attracting global attention, especially in the fields of energy conversion and storage. To date, research has focused on transitionmetal and precious-metal-bas...

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Structural, elastic, vibrational and electronic properties of amorphous Sm2O3 from Ab Initio calculations

Cited by 15 publications

References 93 publications

Disorder-induced electron and hole trapping in amorphous TiO2

Disorder-induced electron and hole trapping in amorphous TiO2

Review: understanding the properties of amorphous materials with high-performance computing methods

Rare‐Earth Single‐Atom Catalysts: A New Frontier in Photo/Electrocatalysis

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