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Amorphous materials inherit short- and medium-range order from the corresponding crystal and thus preserve some of its properties while still exhibiting novel properties.sup.1,2. Due to its important applications in technology, amorphous carbon with sp.sup.2 or mixed sp.sup.2-sp.sup.3 hybridization has been explored and prepared.sup.3,4, but synthesis of bulk amorphous carbon with sp.sup.3 concentration close to 100% remains a challenge. Such materials inherit the short-/medium-range order of diamond and should also inherit its superior properties.sup.5. Here, we successfully synthesized millimetre-sized samples--with volumes 10.sup.3-10.sup.4 times as large as produced in earlier studies--of transparent, nearly pure sp.sup.3 amorphous carbon by heating fullerenes at pressures close to the cage collapse boundary. The material synthesized consists of many randomly oriented clusters with diamond-like short-/medium-range order and possesses the highest hardness (101.9 [plus or minus] 2.3 GPa), elastic modulus (1,182 [plus or minus] 40 GPa) and thermal conductivity (26.0 [plus or minus] 1.3 W m.sup.-1 K.sup.-1) observed in any known amorphous material. It also exhibits optical bandgaps tunable from 1.85 eV to 2.79 eV. These discoveries contribute to our knowledge about advanced amorphous materials and the synthesis of bulk amorphous materials by high-pressure and high-temperature techniques and may enable new applications for amorphous solids. Preparing amorphous phases of carbon with mostly sp.sup.3 bonding in bulk is challenging, but macroscopic samples that are nearly pure sp.sup.3 are synthesized here by heating fullerenes at high pressure., Author(s): Yuchen Shang [sup.1] , Zhaodong Liu [sup.1] [sup.2] , Jiajun Dong [sup.1] , Mingguang Yao [sup.1] , Zhenxing Yang [sup.1] , Quanjun Li [sup.1] , Chunguang Zhai [sup.1] , [...]

Ultrahigh-temperature–pressure experiments are crucial for understanding the physical and chemical properties of matter. The recent development of boron-doped diamond (BDD) heaters has made such melting experiments possible in large-volume presses. However, estimates of temperatures above 2600 K and of the temperature distributions inside BDD heaters are not well constrained, owing to the lack of a suitable thermometer. Here, we establish a three-dimensional finite element model as a virtual thermometer to estimate the temperature and temperature field above 2600 K. The advantage of this virtual thermometer over those proposed in previous studies is that it considers both alternating and direct current heating modes, the actual sizes of cell assemblies after compression, the effects of the electrode, thermocouple and anvil, and the heat dissipation by the pressure-transmitting medium. The virtual thermometer reproduces the power–temperature relationships of ultrahigh-temperature–pressure experiments below 2600 K at press loads of 2.8–7.9 MN (∼19 to 28 GPa) within experimental uncertainties. The temperatures above 2600 K predicted by our virtual thermometer are within the uncertainty of those extrapolated from power–temperature relationships below 2600 K. Furthermore, our model shows that the temperature distribution inside a BDD heater (19–26 K/mm along the radial direction and <83 K/mm along the longitudinal direction) is more homogeneous than those inside conventional heaters such as graphite or LaCrO3 heaters (100–200 K/mm). Our study thus provides a reliable virtual thermometer for ultrahigh-temperature experiments using BDD heaters in Earth and material sciences. [ABSTRACT FROM AUTHOR]

Anaerobic digestion is an important means to turn agricultural waste into resources and an important way to address the challenges in treating vegetable residues in China. In this study, the co-digestion of dairy manure with tomato residue was investigated to clarify the effect of the total solids (TS) of the digestion substrate on methane's production and mechanism using the self-made anaerobic digestion device. The results showed that all treatments could rapidly ferment methane and that the daily methane production showed a trend of increasing first and then decreasing. The optimal concentrations of the digestion substrate for liquid anaerobic digestion (L-AD), hemi-solid-state anaerobic digestion (HSS-AD), and solid-state anaerobic digestion (SS-AD) were 10%, 18%, and 25%, respectively. Compared with SS-AD and HSS-AD, L-AD gas production peaked 3–6 days earlier. Treatment TS25 had the best cumulative methane production, reaching 117.4 mL/g VS. However, treatment TS6 had acid accumulation and a very unstable system. The cumulative methane production of SS-AD was higher than that of HSS-AD and L-AD. Firmicutes and Bacteroidetes were the dominant flora, and Methanoculleus, Methanosarcina, and Methanobrevibacter were the main archaeal groups. The TS significantly changed the microbial community composition of the digestion system, especially the low TS treatment. The results presented herein indicated that TS significantly changed the bacterial and archaeal community composition of the digestion system, and thus with the increase in TS from 6% to 25%, the methane yield increased. [ABSTRACT FROM AUTHOR]

As an advanced amorphous material, sp3 amorphous carbon exhibits exceptional mechanical, thermal and optical properties, but it cannot be synthesized by using traditional processes such as fast cooling liquid carbon and an efficient strategy to tune its structure and properties is thus lacking. Here we show that the structures and physical properties of sp3 amorphous carbon can be modified by changing the concentration of carbon pentagons and hexagons in the fullerene precursor from the topological transition point of view. A highly transparent, nearly pure sp3−hybridized bulk amorphous carbon, which inherits more hexagonal-diamond structural feature, was synthesized from C70 at high pressure and high temperature. This amorphous carbon shows more hexagonal-diamond-like clusters, stronger short/medium-range structural order, and significantly enhanced thermal conductivity (36.3 ± 2.2 W m−1 K−1) and higher hardness (109.8 ± 5.6 GPa) compared to that synthesized from C60. Our work thus provides a valid strategy to modify the microstructure of amorphous solids for desirable properties. sp3 amorphous carbon exhibits exceptional mechanical, thermal, and optical properties, but cannot be synthesized using traditional processes. Here authors report a nearly pure sp3−hybridized amorphous carbon synthesized from C70 which shows more short/medium-range order and enhanced thermal conductivity compared to C60. [ABSTRACT FROM AUTHOR]

This paper focuses on reviewing past progress in the advancement of definitions, methods, and models for safety analysis and assessment of process industrial systems and highlighting the main research topics. Based on the analysis of the knowledge with respect to process safety, the review covers the fact that the entire system does not have the ability to produce casualties, health deterioration, and other accidents, which ultimately cause human life threats and health damage. And, according to the comparison between safety and reliability, when a system is in an unreliable state, it must be in an unsafe state. Related works show that the main organizations and regulations are developed and grouped together, and these are also outlined in the literature. The progress and current research topics of the methods and models have been summarized and discussed in the analysis and assessment of safety for process industrial systems, which mainly illustrate that the dynamic operational safety assessment under the big data challenges will become the research direction, which will change the future study situation. [ABSTRACT FROM AUTHOR]

Data assimilation techniques are one of the most important ways to reduce the uncertainty in atmospheric chemistry model input and improve the model forecast accuracy. In this paper, an ensemble optimal interpolation assimilation (EnOI) system for a regional online chemical weather numerical forecasting system (GRAPES_Meso5.1/CUACE) is developed for operational use and efficient updating of the initial fields of chemical components. A heavy haze episode in eastern China was selected, and the key factors affecting EnOI, such as localization length scale, ensemble size, and assimilation moment, were calibrated by sensitivity experiments. The impacts of assimilating ground-based PM 2.5 observations on the model chemical initial field PM 2.5 and visibility forecasts were investigated. The results show that assimilation of PM 2.5 reduces the uncertainty in the initial PM 2.5 field considerably. Using only 50 % of observations in the assimilation, the root mean square error (RMSE) of initial PM 2.5 for independent verification sites in mainland China decreases from 73.7 to 46.4 µ g m -3 , and the correlation coefficient increases from 0.58 to 0.84. An even larger improvement appears in northern China. For the forecast fields, assimilation of PM 2.5 improves PM 2.5 and visibility forecasts throughout the time window of 24 h. The PM 2.5 RMSE can be reduced by 10 %–21 % within 24 h, and the assimilation effect is the most remarkable in the first 12 h. Within the same assimilation time, the assimilation efficiency varies with the discrepancy between model forecasts and observations at the moment of assimilation, and the larger the deviation, the higher the efficiency. The assimilation of PM 2.5 further contributes to the improvement of the visibility forecast. When the PM 2.5 increment is negative, it corresponds to an increase in visibility, and when the PM 2.5 analysis increment is positive, visibility decreases. It is worth noting that the improvement of visibility forecasting by assimilating PM 2.5 is more obvious in the light-pollution period than in the heavy-pollution period. The results of this study show that EnOI may provide a practical and cost-effective alternative to the ensemble Kalman filter (EnKF) for the applications where computational cost is the main limiting factor, especially for real-time operational forecast. [ABSTRACT FROM AUTHOR]

Although China's air quality has substantially improved in recent years due to the vigorous emissions reduction, the Beijing–Tianjin–Hebei (BTH) region, especially its central and southern plains at the eastern foot of the Taihang Mountains, has been the most polluted area in China, with persistent and severe haze in winter. Combining meteorology–chemistry coupled model simulations and multiple observations, this study explored the causes of several heavy haze events in this area in January 2017, focusing on local circulations related to mountain terrain. The study results showed that on the weather scale, the configuration of the upper, middle, and lower atmosphere provided favorable weather and water vapor transport conditions for the development of haze pollution. Under the weak weather-scale systems, local circulation played a dominant role in the regional distribution and extreme values of PM 2.5. Influenced by the Taihang and Yanshan mountains, vertical circulations and wind convergence zone were formed between the plain and mountain slopes. The vertical distribution of pollutants strongly depended on the intensity and location of the circulation. The circulation with high intensity and low altitude was more unfavorable for the vertical and horizontal diffusion of near-surface pollutants. More importantly, we found that the aerosol–radiation interaction (ARI) significantly amplified the impacts of local vertical circulations on heavy haze by two mechanisms. First, the ARI strengthened the vertical circulations at the lower levels, with the zonal wind speeds increasing by 0.3–0.8 m s -1. Meanwhile, the ARI could cause a substantial downward shift in the vertical circulations (∼ 100 m). Second, the ARI weakened the horizontal diffusion of pollutants by reducing the westerly winds and enhancing wind convergence and southerly winds. Under these two mechanisms, pollutants could only recirculate in a limited space. This superposition of the typical local circulation and the ARI eventually contributed to the accumulation of pollutants and the consequent deterioration of haze pollution in the region. [ABSTRACT FROM AUTHOR]

Reliable observations of aerosol optical properties are crucial for quantifying the radiative forcing of climate. The simultaneous measurements of aerosol optical properties at three wavelengths for PM 1 and PM 10 were conducted in urban Beijing from March 2018 to February 2022. The aerosol absorption coefficient (σab) at 550 nm of PM 10 and PM 1 decreased by 55.0 % and 53.5 % from 2018 to 2021. The significant reduction in σab may be related to reduced primary emissions caused by effective air pollution control measures. PM 2.5 mass concentration decreased by 34.4 % from 2018 to 2021. Single scattering albedo (SSA) increased from 0.89±0.04 for PM 10 (0.87±0.05 for PM 1) in 2018 to 0.93±0.03 for PM 10 (0.91±0.04 for PM 1) in 2021. Increasing SSA and decreasing PM 2.5 mass concentration suggest that the fraction of absorbing aerosols decreased with improved air quality due to pollution control measures being taken. The annual average submicron absorption ratio (Rab) increased from 86.1 % in 2018 to 89.2 % in 2021, suggesting that fine particles are the main contributors to total PM 10 absorption and that the contribution of fine particles to absorption became more important. The absorption Ångström exponent (AAE) in winter decreased from 2018 to 2021, implying a decreasing contribution from brown carbon to light absorption, which may relate to the reduced emissions of biomass burning and coal combustion. During the study period, aerosol radiative forcing efficiency became more negative, mainly influenced by increasing SSA and was -27.0 and -26.2 W m -2 per aerosol optical depth (AOD) for PM 10 and PM 1 in 2021. Higher σab and PM 2.5 mass concentrations were primarily distributed in clusters 4 and 5, transported from the south and the west of Beijing each year. σab and PM 2.5 corresponding to clusters 4 and 5 decreased evidently from 2018 to 2021, which may result from the control of source emissions in surrounding regions of Beijing. The 4-year data presented in this study provide critical optical parameters for radiative forcing assessment within two size ranges and are helpful for evaluating the effectiveness of clean air action. [ABSTRACT FROM AUTHOR]

Laboratory measurements of sound velocities of high-pressure minerals provide crucial information on the composition and constitution of the deep mantle via comparisons with observed seismic velocities. Calcium silicate (CaSiO.sub.3) perovskite (CaPv) is a high-pressure phase that occurs at depths greater than about 560 kilometres in the mantle.sup.1 and in the subducting oceanic crust.sup.2. However, measurements of the sound velocity of CaPv under the pressure and temperature conditions that are present at such depths have not previously been performed, because this phase is unquenchable (that is, it cannot be physically recovered to room conditions) at atmospheric pressure and adequate samples for such measurements are unavailable. Here we report in situ X-ray diffraction and ultrasonic-interferometry sound-velocity measurements at pressures of up to 23 gigapascals and temperatures of up to 1,700 kelvin (similar to the conditions at the bottom of the mantle transition region) using sintered polycrystalline samples of cubic CaPv converted from bulk glass and a multianvil apparatus. We find that cubic CaPv has a shear modulus of 126 [plus or minus] 1 gigapascals (uncertainty of one standard deviation), which is about 26 per cent lower than theoretical predictions.sup.3,4 (about 171 gigapascals). This value leads to substantially lower sound velocities of basaltic compositions than those predicted for the pressure and temperature conditions at depths between 660 and 770 kilometres. This suggests accumulation of basaltic crust in the uppermost lower mantle, which is consistent with the observation of low-seismic-velocity signatures below 660 kilometres.sup.5,6 and the discovery of CaPv in natural diamond of super-deep origin.sup.7. These results could contribute to our understanding of the existence and behaviour of subducted crust materials in the deep mantle.In situ high-pressure and high-temperature measurements of the sound velocity of CaSiO.sub.3 perovskite suggest accumulation of basaltic crust in the Earth's uppermost lower mantle., Author(s): Steeve Gréaux [sup.1] [sup.2] , Tetsuo Irifune [sup.1] [sup.2] , Yuji Higo [sup.3] , Yoshinori Tange [sup.3] , Takeshi Arimoto [sup.1] , Zhaodong Liu [sup.1] , Akihiro Yamada [sup.1] [...]

Akimotoite, a MgSiO3 polymorph present in the lower transition zone within ultramafic portions of subducting slabs and potentially also in the ambient mantle, will partition some amount of Al, raising the question of how this will affect its crystal structure and properties. In this study, a series of samples along the MgSiO3-Al2O3 (akimotoite-corundum) solid solution have been investigated by means of single-crystal X-ray diffraction to examine their crystal chemistry. Results show a strong nonlinear behavior of the a-and oaxes as a function of Al content, which arises from fundamentally different accommodation mechanisms in the akimotoite and corundum structures. Furthermore, two Al2O3- bearing akimotoite samples were investigated at high pressure to determine the different compression mechanisms associated with Al substitution. Al2O3-bearing akimotoite becomes more compressible at least up to 20 mol% Al2O3, due likely to an increase in compressibility as the Al cation is incorporated into the SiO6 octahedron. This observation is in strong contrast to the stiffer corundum end-member having a KT = 250 GPa, which is larger than that of the akimotoite end-member [KT = 205(1) GPa]. These findings have implications for mineral physics models of elastic properties, which have in the past assumed linear mixing behavior between the MgSiO3 akimotoite and Al2O3 corundum end-members to calculate sound wave velocities for Al-bearing akimotoite at high pressure and temperature. [ABSTRACT FROM AUTHOR]

The representation of aerosol–cloud interaction (ACI) and its impacts in the current climate or weather model remains a challenge, especially for severely polluted regions with high aerosol concentration, which is even more important and worthy of study. Here, ACI is first implemented in the atmospheric chemistry model GRAPES_Meso5.1/CUACE by allowing for real-time aerosol activation in the Thompson cloud microphysics scheme. Two experiments are conducted focusing on a haze pollution case with coexisting high aerosol and stratus cloud over the Jing–Jin–Ji region in China to investigate the impact of ACI on the mesoscale numerical weather prediction (NWP). Study results show that ACI increases cloud droplet number concentration, water mixing ratio, liquid water path (CLWP), and optical thickness (COT), as a result improving the underestimated CLWP and COT (reducing the mean bias by 21 % and 37 %, respectively) over a certain subarea by the model without ACI. A cooling in temperature in the daytime below 950 hPa occurs due to ACI, which can reduce the mean bias of 2 m temperature in the daytime by up to 14 % (∼ 0.6 ∘ C) in the subarea with the greatest change in CLWP and COT. The 24 h cumulative precipitation in this subarea corresponding to moderate-rainfall events increases, which can reduce the mean bias by 18 %, depending on the enhanced melting of the snow by more cloud droplets. In other areas or periods with a slight change in CLWP and COT, the impact of ACI on NWP is not significant, suggesting the inhomogeneity of ACI. This study demonstrates the critical role of ACI in the current NWP model over the severely polluted region and the complexity of the ACI effect. [ABSTRACT FROM AUTHOR]

Silicate glass has been used as an analog for silicate melts to understand the nature of dense magmas in the Earth's mantle. To understand the effect of Al2O3 on the sound velocity and structure of MgSiO3 glass, in this study, combined with Brillouin scattering and diamond anvil cells (DACs), the acoustic velocity of MgSiO3∙5 mol%Al2O3 (MA1) and MgSiO3∙24.5 mol%Al2O3 (MA2) glass were measured up to 20 and 42 GPa, respectively. Our studies show that the incorporation of Al2O3 could increase the sound velocity of MgSiO3 glass. Using the obtained velocities, the bulk and shear moduli (KS, G), density (ρ) and Poisson's ratio (ν) are calculated at high pressures, and the results indicate that Al2O3 could induce the stiffness of MgSiO3 glass. However, the effect of Al2O3 content on the stiffness of MgSiO3 glass is non-linear, and MA1 and MA2 exhibit similar KS and G at high pressures. With the increase of pressure, the transverse acoustic mode (VS) of MA1 and MA2 shows abnormal changes at 17.8 GPa and 31.8 GPa, which are related to the transition of coordination number (CN) for Si-O in Al-bearing MgSiO3 glass. Compared with previous studies on sound velocity of MgSiO3 glass, the incorporation of Al2O3 delays the transition pressure of Si-O coordination to a higher pressure. Our study has profound implications for understanding the density and sound velocity of Al-bearing MgSiO3 melt in the Earth's interior. [ABSTRACT FROM AUTHOR]

Penetrating, high‐energy synchrotron X‐rays are in strong demand, particularly for high‐pressure research in physics, chemistry and geosciences, and for materials engineering research under less extreme conditions. A new high‐energy wiggler beamline P61 has been constructed to meet this need at PETRA III in Hamburg, Germany. The first part of the paper offers an overview of the beamline front‐end components and beam characteristics. The second part describes the performance of the instrumentation and the latest developments at the P61B endstation. Particular attention is given to the unprecedented high‐energy photon flux delivered by the ten wigglers of the PETRA III storage ring and the challenges faced in harnessing this amount of flux and heat load in the beam. Furthermore, the distinctiveness of the world's first six‐ram Hall‐type large‐volume press, Aster‐15, at a synchrotron facility is described for research with synchrotron X‐rays. Additionally, detection schemes, experimental strategies and preliminary data acquired using energy‐dispersive X‐ray diffraction and radiography techniques are presented. [ABSTRACT FROM AUTHOR]

(1-x)(0.75Na0.5Bi0.5TiO3-0.25SrTiO3)-xErBiO3 (NBST-xEB, x = 0–0.04) ceramics were fabricated through a solid state reaction method. Scanning electron microscopy investigation shows that grain size of the ceramics decreases with increasing x. X-ray diffraction results reveal that all the ceramics are pseudocubic phase. An enhanced disordering of local structure by EB doping is revealed by Raman spectra. The NBST-xEB ceramics exhibit excellent dielectric stability within a wide temperature range after EB doping. A relatively high recoverable energy storage density (Wrec) of 1.834 J/cm3 with efficiency (η) of 71% are obtained for NBST-0.02 EB ceramics under a moderate electric field of 148 kV/cm. The Wrec and η of the NBST-0.02 EB ceramics exhibit excellent fatigue stability (104) and temperature stability (Wrec > 0.834 J/cm3, η > 64%) within 30–200 °C under 100 kV/cm. With the introduction of EB, the NBST-xEB ceramics also show strong photoluminescence properties due to the presence of Er3+. [ABSTRACT FROM AUTHOR]

MgSiO3 majorite is the most significant endmember of the Al‐deficient majorite garnets that form at depths higher than ∼400 km, in the mantle transition zone (MTZ). Here, we report elastic wave velocity measurements on polycrystalline MgSiO3 majorite samples, up to 18.4 GPa and 2000 K by ultrasonic interferometry techniques combined with in situ X‐ray diffraction measurements in a multianvil apparatus. Our data show MgSiO3 majorite has the lowest elastic moduli among silicate garnet endmembers, under the pressure and temperature conditions of the MTZ. These new data combined with those of other garnet endmembers allowed to estimate VP and VS of majorite with compositions relevant to the MTZ. The results suggest that variation of MgSiO3 component in garnet may play a role for interpreting seismic gradients atop the 410‐km discontinuity while below ∼520 km, the velocity contrasts hold too low values to explain the discrepancy between mineral physics data and seismological observations. Plain Language Summary: Majorite is an important constituent of mantle garnet that form at depths higher than ∼400 km, in the Earth's mantle transition zone. Here, we report elastic wave velocity measurements on polycrystalline MgSiO3 majorite samples, up to 18.4 GPa and 2000 K by ultrasonic interferometry techniques combined with in situ X‐ray diffraction measurements in a multianvil apparatus. Our data show MgSiO3 majorite has the lowest elastic moduli among other silicate garnets and therefore may play a role for interpreting the steep seismic gradients across the 410‐km discontinuity while below ∼520 km, it holds too low seismic contrast to explain the discrepancy between mineral physics data and seismological observations. Key Points: Sound velocities of MgSiO3 majorite were measured up to 18.4 GPa and 2000 KElastic softening increase gradually upon increasing MgSiO3 content in mantle garnetsPyrolite and mid‐ocean ridge basalts majorite are unlikely to explain the high VP and VS of the bottom mantle transition region [ABSTRACT FROM AUTHOR]

The traditional reclosing device cannot distinguish the fault nature of blind reclosing, which will cause secondary damage to the faulty power system. In addition, the existence of fault resistance makes fault location complicated. This paper proposes an automatic reclosing device which enters the fault line through the single-phase AC voltage signal of the power electronic converter. The device responds to the comprehensive utilization of the system harmonic impedance and locates the fault current through the comprehensive utilization of the system harmonic impedance judgment. So, the device can eliminate the influence of fault resistance for positioning the result. Because the measurement is performed only at the head-end circuit, no communication line is required. If a permanent fault is found in the system, the fault information and the latching circuit breaker should be indicated. If there is no fault notification, the circuit breaker should be switched. The equipment has been proved to have accurate identification to detect the results of various fault types, so it can avoid the secondary damage of the power system caused by blind reclosing. [ABSTRACT FROM AUTHOR]

This study addresses the non‐fragile controller design of a class of fractional‐order (FO) linear delayed systems assumed to have structured uncertainties in both the plant and the controller. By using the linear matrix inequality method, singular value decomposition and FO Razumikhin theorem, the delay‐dependent and order‐dependent robust non‐fragile state feedback controller and non‐fragile observer‐based robust state feedback controller are synthesised, respectively, based on whether the states are available or not. Three examples are presented to verify the effectiveness of the proposed schemes. [ABSTRACT FROM AUTHOR]

This paper investigates the event-triggered containment control problem of a class of uncertain nonlinear multiagent systems (MASs). By employing the local relative information, we design an adaptive event-triggered containment algorithm. The proposed containment algorithm can cope with the unavailability of global topology information and uncertain dynamics of follower agents. Therefore, the presented containment algorithm is free of global topology information, i.e., the designed algorithm is fully distributed. In addition, it is proved that Zeno behavior will not occur. At last, a numerical example is given to verify our event-triggered containment algorithm. [ABSTRACT FROM AUTHOR]

Oxygen vacancies (OVs), that charge‐balance the replacement of octahedrally coordinated Si4+ by Al3+ in the mineral bridgmanite, will influence transport properties in the lower mantle but little is known about their stability and local structure. Using 27Al nuclear magnetic resonance (NMR) spectroscopy we have characterized OVs within six aluminous bridgmanite samples. In the resulting NMR spectra sixfold, fivefold, and fourfold coordinated Al species are resolved, in addition to near eightfold coordinated Al substituting for Mg. Fivefold coordinated Al is formed by single OV sites but fourfold coordination must result from short range ordering of OVs, producing OV clusters that may form through migration into twin domain walls. Characterizing the occurrence of such OV structures is an important prerequisite for understanding how transport properties change with depth and composition in the lower mantle. Plain Language Summary: The lower mantle encompasses the largest region of the Earth's interior and is mainly composed of the perovskite‐structured mineral (Mg,Fe,Al)(Al,Si)O3 bridgmanite. Its properties, therefore, control both the diffusive transport of elements and solid state flow in the lower mantle, which will be strongly influenced by point defects. We have identified and quantified defects in bridgmanite that arise from the replacement of silicon by aluminum and result in the creation of a vacant oxygen site. These oxygen defects are also found to form clusters in the structure, which in other perovskite structured minerals have been shown to strongly affect physical properties. As defect formation and ordering is dependent on composition and pressure, strong variations in physical properties may be expected within the upper 300 km of the lower mantle. Key Points: Al substitution in bridgmanite is dominated by the oxygen vacancy mechanism for peridotite mantle compositionsShort‐range ordering of oxygen vacancies takes place forming oxygen vacancy clusters possibly due to migration into twin domain wallsOxygen vacancy clusters are expected to have a major influence on transport properties of the lower mantle, such as the electrical conductivity [ABSTRACT FROM AUTHOR]