Oxygen Triclusters Research Articles

Transformations to the aluminum coordination environment and network polymerization in amorphous aluminosilicates under pressure.

The structure of calcium aluminosilicate glasses (CaO)x(Al2O3)y(SiO2)1-x-y with the near tectosilicate compositions x ≃ 0.19 and 1 - x - y ≃ 0.61 or x ≃ 0.26 and 1 - x - y ≃ 0.49 was investigated by in situ high-pressure neutron diffraction and 27Al nuclear magnetic resonance (NMR) spectroscopy. The results show three distinct pressure regimes for the transformation of the aluminum coordination environment from tetrahedral to octahedral, which map onto the deformations observed in the production of permanently densified materials. The oxygen packing fraction serves as a marker for signaling a change to the coordination number of the network forming motifs. For a wide variety of permanently densified aluminosilicates, the aluminum speciation shares a common dependence on the reduced density ρ' = ρ/ρ0, where ρ is the density and ρ0 is its value for the uncompressed material. The observed increase in the Al-O coordination number with ρ' originates primarily from the formation of six-coordinated aluminum Al(VI) species, the fraction of which increases rapidly beyond a threshold ρthr'∼ 1.1. The findings are combined to produce a self-consistent model for pressure-induced structural change. Provided the glass network is depolymerized, one-coordinated non-bridging oxygen atoms are consumed to produce two-coordinated bridging oxygen atoms, thus increasing the network connectivity in accordance with the results from 17O NMR experiments. Otherwise, three-coordinated oxygen atoms or triclusters appear, and their fraction is quantified by reference to the mean coordination number of the silicon plus aluminum species. The impact of treating Al(VI) as a network modifier is discussed.

Molecular insight into the structural and mechanical properties of Ca-based geopolymers

Ca-based geopolymers are a principal product of introducing calcium into geopolymers. Analyzing Ca-based geopolymers structural and mechanical properties aids in optimizing mix design of geopolymers. In this paper, partially reacted low-polymerization and fully reacted high-polymerization models were constructed to examine the structural and mechanical properties of Ca-based geopolymers with varying calcium contents via molecular dynamics simulations. Results show that Ca-based geopolymers contain pentacoordinate aluminum and tricluster oxygen which is more brittle and makes the structure loose. In low-polymerization models, an increase in calcium content accelerates the polymerization rate by overcoming the low-temperature reaction barrier. However, calcium content hinders the formation of pentacoordinate aluminum, decreasing the final degree of polymerization, resulting in weakened mechanical properties. In high-polymerization models, increased calcium decreases tricluster oxygen content, resulting in improved mechanical properties. While the hydrolysis reaction reduces mechanical properties, the weakening effect of water is greater than the enhancing effect of calcium.

Effect of compression temperature on the structure and properties of hot compressed sodium borosilicate glasses from molecular dynamics simulations

Applying pressure during glass formation or annealing is an effective method to modify the properties of oxide glasses. The effect of compression temperature on the structure and properties of a sodium borosilicate glass has been investigated using molecular dynamics simulations. The connection between macroscopic properties (density and elastic moduli) and microscopic structures (short- and medium-range order) was investigated. Young’s modulus increased with the compression temperature and then reached a plateau at temperatures close to the glass transition temperature. The modulus increase was found to correlate linearly with glass density change. Correlations with structural changes, such as fraction of four-fold coordinated boron, oxygen triclusters, sodium ion coordination number and the Na–O and Na–Na distances were studied. The results suggest that the pressure-induced transformation from three-fold to four-fold coordinated boron was achieved through the formation of oxygen triclusters, which is different from the commonly observed mechanism involving nonbridging oxygen during the boron coordination change. In addition, the linear correlation between sodium coordination number and glass density suggests that change of sodium ion local environment and redistribution of sodium ions also play an important role in the property behaviour during pressure quenching of the glasses.

Molecular dynamics simulations of magnesium aluminosilicate glass structure: High‐coordinated alumina and oxygen tricluster formation

AbstractPrevious research has shown a consistent discrepancy in the reported structure of alkaline earth aluminosilicate glasses using molecular dynamics (MD) simulations versus nuclear magnetic resonance (NMR) experiments. Past MD results have consistently shown less than 5% five‐coordinated Al units (Al[5]) in peraluminous glass compositions, but with high fractions of triple‐bonded oxygens (TBO, i.e., triclusters). Experimental results have shown a high fraction of Al[5] with no direct evidence for TBO. One of the main criticisms associated with high TBO content found in MD‐generated glass structures is the use of classical interatomic potentials. To investigate this issue, we analyze the formation of both TBO and Al[5] using three independently developed potentials with varying silica content and [Al2O3]/[MgO] ratios for the magnesium aluminosilicate (MAS) system. We specifically choose compositions with high ratios of alumina to magnesium oxide as this region is not as commonly explored. Results indicate that Al[5] charge compensates the Al network in metaluminous compositions (compositions with more Mg than Al) while both TBO and Al[5] are prevalent in peraluminous ranges (high Al content compositions) to charge balance Al units. From the literature, NMR experiments report MAS glasses with varying Al[5] fractions and show significant differences for the same reported compositions. When comparing MD results from this work, the fraction of calculated Al[5] is within the experimental variation found in the literature. This indicates that classical potentials can accurately capture alumina environments and that both Al[5] and TBO can coexist in relatively high fractions. From the consistency in our results, we conclude that TBOs are inherent to the aluminosilicate glass system and are not simulation artifacts.

Molecular dynamics simulations study on structure and elastic property of alkali-free aluminoborosilicate glasses with different Al2O3/(MgO+CaO) ratio

The effect of Al2O3/(MgO+CaO) ratio on structure and elastic modulus of CaO-MgO-Al2O3-B2O3-SiO2 (CMABS) glasses were investigated by combining molecular dynamics simulations, Makishima-Mackenzie model and experiments. With the increase of Al2O3/(CaO+MgO) ratio, the main coordination number of Al3+ and Si4+ was four, while more than 79 % of B3+ existed in the form of [BO3]. The bridging oxygen and tri-cluster oxygen showed an overall increasing trend and the large rings transformed into smaller rings, both of which indicated the increaseing network connectivity and network polymerization. The dissociation energy of glass samples also showed an increasing trend. Therefore, with the increase of network polymerization and dissociation energy, the elastic modulus increased from 83.2 GPa to 89.85 GPa. The elastic modulus of CMABS glasses calculated by the molecular dynamics simulations and Makishima-Mackenzie model differ within 10 % from the values tested, and they have the same trend of variation.

Oxygen tri-clusters make glass highly crack-resistant

Identifying key structural factors that surmount their intrinsic brittleness and poor crack initiation resistance (CR) is crucial for designing glass efficiently and predictably. In this study, we present three significant discoveries that contribute to the design of glasses with superior mechanical performances. Firstly, the CR of the aluminosilicate glasses exhibited a drastic increase when the alumina content surpasses a critical threshold. Secondly, the fraction of three-coordinated oxygens (i.e., oxygen tri-cluster fraction [(3)O]) was successfully quantified using our new Nuclear Magnetic Resonance technique. Thirdly, a correlation between the evolution trend of the [(3)O] and the alumina content was established, which aligns closely with the CR trend. These findings suggest that oxygen tri-clusters play a crucial role in significantly enhancing CR in aluminosilicate glasses.

Mg and Al mixed effects on thermal properties in aluminosilicate glasses

AbstractBy using the aerodynamic levitation and laser melting technique to well extend the glass‐forming region into the Mg‐rich and peraluminous regime, a series of magnesium aluminosilicate glasses were prepared to investigate the Mg and Al mixed effects on thermal properties, including glass transition temperature (Tg), crystallization behavior, and thermal stability. With the gradual substitution of Mg by Al, Tg exhibits two types of near‐linear rises with different slopes in two compositional regions separated by r = 0.57, where r is equal to the molar ratio of [Al2O3]/([Al2O3] + [MgO]). Moreover, when it comes to other properties, that is, crystallization behavior and thermal stability, this critical point precisely appears at the same r = 0.57. Compared to the slower increase of Tg in Mg‐rich region, the steeper rise of Tg in the peraluminous region is mainly ascribed to the step‐by‐step formation of oxygen triclusters driven by Pauling's second rule. Moreover, the occurrence of the critical point for Tg rise at r = 0.57 rather than the theoretical 0.5 can be seen as a proof of the role of Mg cations partly as a network former.

The structures and properties of yttrium aluminosilicate glasses with low, medium, and high silica contents

Yttrium aluminosilicate glasses with 25–78 mol% silica were studied using molecular dynamics simulations to understand their structural and property changes. The results show that Al3+ ions primarily exist as four-fold coordinated, with <5% in higher-coordinated states that increase with decreasing silica content. The formation of significant concentrations (4–9%) of oxygen tri-clusters and small amounts of free oxygen were also observed, suggesting a perturbed glass network structure. An average Y-O bond distance of 2.26 Å and Y coordination number of 6.3 were found. The glass transition temperatures are relatively insensitive to composition, agreeing with experiments. A 16% and 30% increase in Young's and bulk moduli, respectively, was observed with decreasing silica contents which was explained by the strong Y-O bond and formation of oxygen tri-clusters that aggregate higher coordinated Al species. These results were discussed in the context of optical and acoustic properties of YAS optical fibers that exhibit reduced nonlinearities.

Graph theory-based structural analysis on density anomaly of silica glass

Analyzing the atomic structure of glassy materials is a tremendous challenge both experimentally and computationally, and the lack of direct, detailed insights into glass structure hinders our ability to navigate structure–property relationships. For instance, the structural origin of the density anomaly in silica glasses – the negative thermal expansion coefficient – is still poorly understood. Simulations based on molecular dynamics (MD) produce atomically resolved structures, but quantifying the role of disorder in the density anomaly is challenging. Here, we propose to use a graph-theoretical approach to assess topological differences between disordered structural arrangements from MD trajectories of silica glasses. A graph similarity metric quantifies the similarity between the covalent networks and can characterize the nature of the disordered solid, by comparing to reference crystalline solids, or with glasses in different thermodynamic states. This approach involves casting all-atom glass configurations as networks, and subsequently applying a graph-similarity metric (D-measure). Calculated D-measure values are then taken as the topological distances between two configurations. By measuring the topological distances of silica glass configurations across a range of temperatures, distinct topological features could be observed at temperatures higher than the fictive temperature. In addition, we compared topological distances between local atomic environments in the glass and crystalline silica phases. This approach suggests that more coesite-like and quartz-like local topologies emerge in silica glasses when the density is at a minimum during the heating process. Using graph-based analysis, we then found that the anomalous density behavior of silica glass could be attributed to the moderate increased formation of oxygen triclusters (oxygen coordinated with 3 silicon atoms), and possibly reduced number of larger sized cycles at the density minimum temperature.

Modeling Oxygen Tricluster Formation in Calcium Aluminosilicate Supercooled Liquids and Glasses.

Calcium aluminosilicate glasses have technological importance for a variety of industrial applications. However, the short-range structure of this glass system remains widely debated regarding the formation of oxygen triclusters. It is argued that triclusters are observed in high percentages within molecular dynamics simulations because of the high melting temperatures and correspondingly high fictive temperatures. This work explores the formation of such structural units by first simulating various compositions at different liquid temperatures to understand thermodynamic factors affecting the formation of such species. Structural results are then implemented into a statistical mechanical model which can predict the formation of triclusters at a given fictive temperature. Results show temperature and composition dependence of these structures, with aluminum charge modification favored in the peraluminous regime. It is concluded that oxygen triclusters are the preferred method of charge compensation even when extrapolating to laboratory fictive temperatures, indicating that triclusters are not a byproduct of simulation timescales.

Effect of B2O3 Addition and CaO/Al2O3 Ratios on Melt Structure and Viscosity of CaO–Al2O3-Based Slags

The effect of the addition of B2O3 and the CaO/Al2O3 ratios on the CaO–Al2O3–B2O3 melts’ structure was fully analyzed by molecular dynamics (MD) simulations. The results show that, with the increase in CaO/Al2O3 ratios, the charge compensation for [AlO4]5− tetrahedron changed from the oxygen tricluster structure to the charge provided by Ca2+, and the structure of [AlO4]5− tetrahedron was stabilized. The addition of B2O3 reduced the degree of polymerization of the aluminate melt, which, in turn, lowered the melt viscosity; in the systems with CaO/Al2O3 mole ratio less than 1, the added B2O3 mainly existed in the form of [BO3]3−, which reduced the symmetry and the strength of the melt network structures; in the higher CaO/Al2O3 ratio systems, the depolymerization ability of the addition of B2O3 on aluminate network structures was enhanced with the increase in CaO/Al2O3 ratios, and the overall degree of polymerization of the melt decreased. The viscosity measurement shows that B2O3 lowers the viscosity of CaO–Al2O3 melts, which was consistent with the results predicted by MD simulations.

Composition Dependence of the Atomic Structures and Properties of Sodium Aluminosilicate Glasses: Molecular Dynamics Simulations with Reactive and Nonreactive Potentials.

Understanding the composition-structure-property relations of glass materials is essential for their technological applications. In this study, the structures and properties of a series of sodium aluminosilicate glasses with varying Al2O3/Na2O ratios ((35 - x)Na2O-xAl2O3-65SiO2, x = 0, 5, 10, 15, 17.5, 20) covering peralkaline to peraluminous compositions, have been studied by using molecular dynamics simulations with two types of interatomic potentials: a fixed partial charge pairwise potential (Teter) and a reactive diffusive charge reactive potential (DCRP). The short and medium structural features such as bond lengths, coordination numbers, Qn distributions, and ring size distributions were obtained and compared with experimental data. It was found that silicon remained fourfold-coordinated throughout the compositional range, while a noticeable amount of fivefold-coordinated aluminum together with oxygen triclusters (TBO) are present in compositions with higher Al2O3 contents (RAl/Na > 1). In addition, the simulation results from both potentials show a certain level of violation of the Al avoidance rule by exhibiting a non-negligible amount of [AlOx]-[AlOx] polyhedral connections. Neutron and X-ray diffraction structure factors of the simulated glasses were calculated and compared with available experimental data. The mechanical properties, including Bulk, Shear, and Young's modulus, were calculated and found to increase with increasing RAl/Na, in good agreement with the experiments. Correlations of the properties with glass structures as a function of glass compositions and the advantages as well as potential issues of the two sets of potentials in modeling sodium aluminosilicate glasses are discussed in the context of features of glass structures and the prospect of future simulations of glass-water reactions.

Ab initio molecular dynamics simulation of structural and elastic properties of SiO2–P2O5–Al2O3–Na2O glass

AbstractThe effects of P2O5 content on the structural and mechanical properties of phosphoaluminosilicate glasses were studied using ab initio molecular dynamics simulations. Structural simulations involving the partial radial distribution functions, angle distributions, and proportions of bridging oxygen and nonbridging oxygen species were performed. The results indicated that an increase in the phosphorus content disordered the distributions of the bond length and bond angle. At low phosphorus contents (P2O5 &lt; 5.17 mol%), phosphorus captured sodium ions in the Si–ONBO–Na linkage and formed a P–ONBO–Na linkage, completing the silicate network. With P2O5 contents ranging from 5.17 mol% to 8.62 mol%, PO4 units existed in the glass network in the form of Si–OBO–P and Al–OBO–P linkages. At higher phosphorus contents (18.97 mol% &lt; P2O5 &lt; 50.00 mol%), silicate glass network transformed into a phosphate glass network, the negative charge generated by AlO4 units was compensated by Al–OBO–P linkage. In particular, the generation mechanisms of oxygen triclusters and five‐coordinate aluminum as well as their evolutions were elaborated. Regarding the mechanical properties, atomic bonding strength was examined to analyze the intrinsic nature of the elastic modulus in phosphoaluminosilicate glass. The results indicated that P‐O bonding strength significantly contributed to the elastic modulus.

Pressure-induced structural evolution in boron-bearing model rhyolitic glasses under compression: Implications for boron isotope compositions and properties of deep melts in Earth’s interior

The pressure-induced structural evolutions of boron-bearing model rhyolitic melts under high pressures enable to infer the detailed geochemical processes (melting and fluid-rock-melt interactions) occurring in Earth interiors and to control the melt properties (viscosity and the boron isotope composition, δ11B) of complex magmatic melts, providing insights into the boron cycle toward the deeper part of the upper mantle (∼10 GPa). Despite the importance, the structures of multicomponent boron-bearing silicate melts above 3 GPa are currently unavailable. Here, we explore the structures, particularly, coordination transformation of constituent elements in boron-bearing nepheline and albite glasses – a model rhyolitic melts - upon compression to a depth of ∼270 km (∼9.2 GPa) in the mantle using multi-nuclear solid-state nuclear magnetic resonance (NMR) spectroscopy. The results showed that the conversion of [3]B into [4]B is prominent upon compression up to 6 GPa. In contrast, the formation of [5,6]Al is accompanied by the formation of oxygen tricluster above 6 GPa, where all the nonbridging oxygens are consumed. We quantify how the melt composition affects tendency to form highly coordinated B, Al, and Si upon compression. Particularly, the increase in the [4]B population tends to be larger for the glasses with low Si content as pressure increases to 9.2 GPa. We reveal the relationship between such structural adaptations of the compressed melts at high pressure and the melt properties, including viscosity and element partition coefficient in boron-bearing melts. The current NMR results also unravel the structural origins of 11B/10B ratios in rhyolitic melts at high pressure. Considering a preferential partitioning of 10B to [4]B, an increase in [4]B population in the melts leads to an pressure-induced enrichment of 10B. As the increase in Si/B ratio in the melts tends to decrease the pressure-induced increase in [4]B fraction, the contribution of boron coordination transformation on the 11B/10B ratios in silicate melt would be somewhat minor in deep mantle melts with increasing Si content. The detailed boron environments in rhyolitic melts at high pressure yield useful constraints for the isotope composition (11B/10B) of dense mantle melts, thereby enabling quantification of deep boron cycle.

Correlation study between microstructure and fluidity of molten slag during co-gasification of coal and indirect coal liquefaction residue: Molecular dynamics simulation

Co-gasification of indirect coal liquefaction residues (ICLR) and coal is an effective way to achieve harmless and sustainable treatment of hazardous wastes. The long-term and stable operation of a co-gasification largely depends on the flow behavior of coal-ash slag. Herein, classical molecular dynamics simulation (MD) and Raman spectroscopy were used to study the microstructure of slag and its relationship with viscosity during the co-gasification of ICLR and coal. The results showed that with the addition of ICLR, the viscosity of slag decreased continuously. This reduction in viscosity was attributed to the increase of FeO content in the system with the addition of ICLR. As a network modifier, FeO could easily provide O2− at high temperatures, thereby destroying bridge oxygen and converting more tricluster oxygen and bridge oxygen into non-bridge oxygen. This significantly reduced the structure complexity and polymerization degree of slag, thereby reducing its viscosity. Finally, the correlation between the microstructural and viscosity was further analyzed. It was found that there was a quadratic function relationship between Q4 proportion and viscosity, and the formula was μ = 0.025(Q4)2-Q4 + 12.03. The purpose of this work was to provide theoretical support for slag flow mechanisms during the gasifier slagging-tapping process and the resource treatment of hazardous wastes.

High‐coordinated alumina and oxygen triclusters in modified aluminosilicate glasses

AbstractAluminosilicate glasses are ubiquitous in high‐performance displays due to their favorable thermal, mechanical, and optical properties. They also exhibit interesting structural features depending on the ratio of alumina to modifiers in the glass system. Excess modifiers exist in the metaluminous region, while the peraluminous region contains more negatively charged alumina structures than modifiers. As the composition switches from metaluminous to peraluminous, anomalous changes in properties such as the glass transition temperature, viscosity, and refractive index occur. This has been explained with two contrasting structural transformations to accommodate the lack of charge‐balancing modifiers: either aluminum increases in coordination (forming five‐coordinated or six‐coordinated Al) and/or oxygens become three‐coordinated (known as triclusters). The precise charge‐balancing mechanism remains a subject of much debate in the community. This review highlights this structural debate by providing a chronological understanding of how these two theories evolved. We also summarize the state‐of‐the‐art understanding of the aluminosilicate glass structure. By gaining a more comprehensive view of the two opposing structural views within the aluminosilicate glass system, we can gain insights on valuable future research from both experimental and modeling perspectives.

Structural model for amorphous aluminosilicates.

An analytical model is developed for the composition-dependent structure of the amorphous aluminosilicate materials (M2O)x(Al2O3)y(SiO2)1-x-y and (MO)x(Al2O3)y(SiO2)1-x-y, where 0 ≤ x ≤ 1 and 0 ≤ y ≤ 1. The model is based on a simple set of reactions and contains a single adjustable parameter p (0 ≤ p ≤ 1). The latter is found from 27Al solid-state nuclear magnetic resonance (NMR) experiments in the regime where R = x/y ≥ 1, aided by new experiments on the magnesium and zinc aluminosilicate systems. The parameter p decreases linearly as the cation field strength of M+ or M2+ increases, as per the observation previously made for the degree of aluminum avoidance [Lee et al., J. Phys. Chem. C 120, 737 (2016)]. The results indicate that as the cation field strength increases, there are less fourfold coordinated aluminum atoms to contribute toward the glass network, and Al-O-Al bonds become more prevalent in a progressive breakdown of Loewenstein's aluminum avoidance rule. The model gives a good account of the composition-dependent fraction of non-bridging oxygen (NBO) atoms for R ≥ 1, as assessed from the results obtained from solid-state NMR experiments. An extension of the model to (M2O3)x(Al2O3)y(SiO2)1-x-y glasses leads, however, to an excess of NBO atoms, the proportion of which can be reduced by invoking network-forming fivefold coordinated Al atoms and/or oxygen triclusters. The model provides a benchmark for predicting the structure-related properties of aluminosilicate materials and a starting point for predicting the evolution in the structure of these materials under the extreme conditions encountered in the Earth's interior or in processes such as sharp-contact loading.

Topological hardening through oxygen triclusters in calcium aluminosilicate glasses

AbstractMolecular dynamics simulations and topological constraint theory are used to study the impact of oxygen triclusters in the calcium aluminosilicate glass system at ratios of 0.6, 1, 1.5, 2, and 4 [Al2O3]/[CaO]. Negligible percentages (less than ~3%) of five‐coordinated Al structures are found at all ratios. Up to ~27% three‐coordinated oxygens, also known as triclusters, are found at the highest ratio of [Al2O3]/[CaO]. A topological constraint model, which considers additional constraints provided by triclusters, is created to predict the glass transition temperature, hardness, and Young's modulus. The models are used to elucidate the role of triclusters in glass properties. Analysis of topological constraints shows that triclusters can potentially increase the glass hardness within the calcium aluminosilicate system. The results are also compared to oxynitride glasses. Triclusters show the same ability as nitrogen to increase the glass hardness but are less effective at increasing the Young's modulus.

Molecular Dynamics Study of Structural Properties of Refining Slag with Various CaO/Al2O3 Ratios

SiO2-Al2O3-CaO-MgO is the main type of refining slag in a ladle furnace. Here the effects of the CaO/Al2O3 mass ratio on the structural properties of the refining slag system are studied by molecular dynamics simulations. The pair distribution function, coordination number, micro-structure unit and diffusion capacity were analyzed. An increase in the CaO/Al2O3 ratio did not change the bond lengths of these units. However, an increase of the CaO/Al2O3 ratio caused more charge compensators to be introduced into the refining slag system, which led to conversion of free oxygen and non-bridging oxygen to tricluster oxygen and bridging oxygen in the system. Moreover, this augmented the content of relatively stable 4- and 5-coordinate Al. As the micro-structure of the system became more complex, the overall diffusion capacity of the refining slag became poorer. In the micro-structure, the diffusion capabilities of different atoms decreased in the following order: Mg &gt; Ca &gt; O &gt; Al &gt; Si.

Principal Vibration Modes of the La2O3-Ga2O3 Binary Glass Originated from Diverse Coordination Environments of Oxygen Atoms.

La2O3-Ga2O3 binary glass exhibits unusual optical properties owing to its high oxygen polarizability and low vibration energy. These optical properties include high refractive indices and a wide transmittance range. In this study, we performed classical molecular dynamics simulations on La2O3-Ga2O3 glass synthesized by an aerodynamic levitation technique. We have obtained structural models that reproduce experimental results, such as NMR, high-energy X-ray diffraction, and neutron diffraction. Based on our analysis, the structural features were clarified: 5-, 6-coordinated Ga, edge-sharing GaOx-GaOx polyhedral linkages, and oxygen triclusters. Additionally, the vibrational density of states was calculated by diagonalization of the dynamical matrix derived from the structural models and the results were compared with Raman scattering spectra. The mode analysis of the Raman spectra revealed that the principal bands at 650 cm-1 were mainly attributed to the stretching modes of the bridging and nonbridging oxygens. Meanwhile, the shoulder bands at the highest frequency of 750 cm-1 were mainly attributed to the stretching modes of the bridging oxygens and oxygen triclusters. The structural models obtained in this study well describe the characteristic local structures and vibrational properties of the La2O3-Ga2O3 glass.