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A General Algorithm for Calculating Irreducible Brillouin Zones

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Communications in Computational Physics 2022年第2期31卷 495-515页

作者： Jeremy J.Jorgensen John E.Christensen Tyler J.Jarvis gus l.w.hart Department of Physics and Astronomy Brigham Young UniversityProvoUtah84602USA Department ofMathematics BrighamYoungUniversityProvoUtah84602USA

Calculations of properties of materials require performing numerical integrals over the Brillouin zone(BZ).Integration points in density functional theory codes are uniformly spread over the BZ(despite integration error being concentrated in small regions of the BZ)and preserve symmetry to improve computational *** points over an irreducible Brillouin zone(IBZ),a rotationally distinct region of the BZ,do not have to preserve crystal symmetry for greater *** freedom allows the use of adaptive meshes with higher concentrations of points at locations of large error,resulting in improved algorithmic *** have created an algorithm for constructing an IBZ of any crystal structure in 2D and *** algorithmuses convex hull and half-space representations for the BZ and IBZ to make many aspects of construction and symmetry reduction of the BZ *** algorithm is simple,general,and available as open-source software.

关键词： Brillouin zone irreducible Brillouin zone

Machine-learned interatomic potentials for alloys and alloy phase diagrams

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npj Computational Materials 2021年第1期7卷 139-147页

作者： Conrad w.Rosenbrock Konstantin Gubaev Alexander VShapeev livia B.Pártay Noam Bernstein Gábor Csányi gus l.w.hart Department of Physics and Astronomy Brigham Young UniversityProvoUTUSA84602 Skolkovo Institute of Science and Technology Skolkovo Innovation CenterNobel Str.3Moscow 143026Russia Department of Chemistry University of ReadingWhiteknightsReading RG66ADUK Department of Chemistry University of WarwickCoventry CV47ALUK US Naval Research laboratory Center for Computational Materials ScienceWashingtonDC 20375USA Department of Engineering University of CambridgeTrumpington StreetCambridge CB21PZUK

we introduce machine-learned potentials for Ag-Pd to describe the energy of alloy configurations over a wide range of *** compare two different *** tensor potentials(MTPs)are polynomial-like functions of interatomic distances and *** Gaussian approximation potential(GAP)framework uses kernel regression,and we use the smooth overlap of atomic position(SOAP)representation of atomic neighborhoods that consist of a complete set of rotational and permutational invariants provided by the power spectrum of the spherical Fourier transform of the neighbor *** types of potentials give excellent accuracy for a wide range of compositions,competitive with the accuracy of cluster expansion,a benchmark for this *** both models are able to describe small deformations away from the lattice positions,SOAP-GAP excels at transferability as shown by sensible transformation paths between configurations,and MTP allows,due to its lower computational cost,the calculation of compositional phase *** the fact that both methods perform nearly as well as cluster expansion but yield off-lattice models,we expect them to open new avenues in computational materials modeling for alloys.

关键词： alloy alloys phase

Machine-learned multi-system surrogate models for materials prediction

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npj Computational Materials 2019年第1期5卷 702-707页

作者： Chandramouli Nyshadham Matthias Rupp Brayden Bekker Alexander V.Shapeev Tim Mueller Conrad w.Rosenbrock Gábor Csányi David w.wingate gus l.w.hart Department of Physics and Astronomy Brigham Young UniversityProvoUT 84602USA Fritz Haber Institute of the Max Planck Society Faradayweg 4–614195 BerlinGermany Skolkovo Institute of Science and Technology Skolkovo Innovation CenterBuilding 3Moscow 143026Russia Department of Materials Science and Engineering Johns Hopkins UniversityBaltimoreMD 21218USA Engineering laboratory University of CambridgeTrumpington StreetCambridge CB21PZUK Computer Science Department Brigham Young UniversityProvoUT 84602USA Citrine Informatics 702 Marshall StreetRedwood CityCA 94063USA

Surrogate machine-learning models are transforming computational materials science by predicting properties of materials with the accuracy of ab initio methods at a fraction of the computational *** demonstrate surrogate models that simultaneously interpolate energies of different materials on a dataset of 10 binary alloys(AgCu,AlFe,AlMg,AlNi,AlTi,CoNi,CuFe,CuNi,FeV,and NbNi)with 10 different species and all possible fcc,bcc,and hcp structures up to eight atoms in the unit cell,15,950 structures in *** find that the deviation of prediction errors when increasing the number of simultaneously modeled alloys isls representations and learning algorithms were found to qualitatively agree on the prediction errors of formation enthalpy with relative errors ofll systems.

关键词： alloys prediction CoNi

Optoelectronic devices based on two-dimensional transition metal dichalcogenides

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Nano Research 2016年第6期9卷 1543-1560页

作者： He Tian Matthew l. Chin Sina Najmaei Qiushi Guo Fengnian Xia hart wang Madan Dubey Ming Hsieh Department of Electrical Engineering University of Southern California Los Angeles California 90089 USA United States Army Research laboratory Maryland 20783-1197 USA Department of Electrical Engineering Yale University Connecticut 06511 USA

In the past few years, two-dimensional （2D） transition metal dichalcogenide （TMDC） materials have attracted increasing attention of the research community, owing to their unique electronic and optical properties, ranging from the valley-spin coupling to the indirect-to-direct bandgap transition when scaling the materials from multi-layer to monolayer. These properties are appealing for the development of novel electronic and optoelectronic devices with important applications in the broad fields of communication, computation, and healthcare. One of the key features of the TMDC family is the indirect-to-direct bandgap transition that occurs when the material thickness decreases from multilayer to monolayer, which is favorable for many photonic applications. TMDCs have also demonstrated unprecedented flexibility and versatility for constructing a wide range of heterostructures with atomic-level control over their layer thickness that is also free of lattice mismatch issues. As a result, layered TMDCs in combination with other 2D materials have the potential for realizing novel high-performance optoelectronic devices over a broad operating spectral range. In this article, we review the recent progress in the synthesis of 2D TMDCs and optoelectronic devices research. we also discuss the challenges facing the scalable applications of the family of 2D materials and provide our perspective on the opportunities offered by these materials for future generations of nanophotonics technology.

关键词： transition metaldichalcogenides (TMDCs),optoelectronic device,molybdenum disulfide(MoS2) photodetector,light-emitting diode (lED)

Disturbance history,species diversity,and structural complexity of a temperate deciduous forest

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Journal of Forestry Research 2020年第2期31卷 397-414页

作者： Jonathan D.Goode Carson R.Barefoot Justin l.hart Daniel C.Dey Department of Geography University of AlabamaTuscaloosaAL 35487USA Northern Research Station USDA Forest ServiceColumbiaMO 65211USA

Stand structural complexity enhancement is an increasingly popular management objective,especially on public *** stand structures are hypothesized to support a relatively high degree of native forest diversity and be more resistant and resilient to *** structures are characterized by the presence of deadwood and heterogeneity of tree-size classes and tree *** little is known about how discrete disturbance events affect structural complexity and compositional diversity in Quercus-dominated stands at fine spatial scales(***).we established 200.05 ha fixed-radius plots on the Sipsey wilderness of william *** National Forest in northern Alabama to quantify woody plant species composition and *** were mapped on each plot to quantify overstory structural complexity and compositional *** extracted two cores from all canopy Quercus spp.C 5 cm diameter at breast height to quantify age,recruitment pulses,and reconstruct canopy disturbance *** species diversity in the sampled area was 1.75 for trees,2.08 for saplings,and 1.69 for *** alba had the greatest basal area,and Ostrya virginiana had the highest *** stand exhibited a reverse J-shaped distribution with a q-factor of *** oldest Quercus dated to 1795,and the largest recruitment pulse occurred in the *** mean return interval for intermediateseverity disturbance was 38 *** we documented no relationships between disturbance frequency and compositional diversity at the neighborhood scale(0.05 ha),less frequent disturbance was associated with higher structural complexity(r^2=0.258,p=0.026)at the neighborhood *** suggest that localized disturbance increases species diversity and structural complexity,but these processes are manifest at the stand level and not at the neighborhood *** conclude that the spatial variability(***,shape,orientation,microsite conditions)is likel

关键词： Canopy gap Quercus(oak) Stand development Succession

Three-dimensional light structure of an upland Quercus stand post-tornado disturbance

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Journal of Forestry Research 2020年第1期31卷 141-153页

作者： Kevin G.willson lauren E.Cox Justin l.hart Daniel C.Dey Department of Geography University of AlabamaTuscaloosaAL 35487USA Department of Environmental Science Policyand ManagementUniversity of CaliforniaBerkeleyCA 94720USA Northern Research Station USDA Forest ServiceColumbiaMO 65211USA

light is the most common limiting factor in forest plant communities,influencing species composition,stand structure,and stand productivity in closed canopy *** vertical light structure is relatively simple under a closed canopy because most light is captured by overstory ***,wind disturbance events create canopy openings from local to landscape scales that increase understory light intensity and vertical light structural *** studied the effects of an EF-1 tornado on horizontal and vertical(***-dimensional)light structure within a Quercus stand to determine how light structure changed with increasing disturbance *** used a two-tiered method to collect photosynthetic photon flux density at 4.67 m and 1.37 m above the forest floor to construct three-dimensional light structure across a canopy disturbance severity gradient to see if light intensity varied with increasing tornado *** indicate that increased canopy disturbance closer to the tornado track increased light penetration and light structure heterogeneity at lower forest *** light intensity correlated with increased sapling density that was more randomly distributed across the plot and had shifted light capture higher in the stand *** penetration through the overstory was most strongly correlated with decreased stem density in the two most important tree species(based on relative dominance and relative density)in the stand,Quercus alba l.(r=-0.31)and Ostrya virginiana(Mill.)***(r=-0.27,plight penetration was most affected by these two *** managers are increasingly interested in patterning silvicultural entries on natural disturbances,they must understand residual stand and light structures that occur after natural disturbance *** providing spatial light data that quantifies light structure post-disturbance,managers can use these results to improve planning required for long-term man

关键词： Photosynthetic photon flux density Midstory Blowdown Heterogeneity

livestock breeding for the 21st century: the promise of the editing revolution

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Frontiers of Agricultural Science and Engineering 2020年第2期7卷 129-135页

作者： Chris PROUDFOOT gus MCFARlANE Bruce wHITElAw Simon lIllICO The Roslin Institute and Royal(Dick)School of Veterinary Studies University of EdinburghEaster BushMidlothianEH259RGUK

In recent years there has been a veritable explosion in the use of genome editors to create sitespecific changes,both in vitro and in vivo,to the genomes of a multitude of species for both basic research and ***,which form a vital component of most societies,are no *** selective breeding has been hugely successful at enhancing some production traits,the rate of progress is often slow and is limited to variants that exist within the breeding *** editing provides the potential to move traits between breeds,in a single generation,with no impact on existing productivity or to develop de novo phenotypes that tackle intractable issues such as *** such,genome editors provide huge potential for ongoing livestock development programs in light of increased demand and disease *** review will highlight some of the more notable agricultural applications of this technology in livestock.

关键词： cattle pig sheep chicken aquaculture CRISPR

California Simulation of Evapotranspiration of Applied water and Agricultural Energy Use in California

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Journal of Integrative Agriculture 2013年第8期12卷 1371-1388页

作者： Morteza N Orang Richard l Snyder Shu Geng Quinn J hart Sara Sarreshteh Matthias Falk Dylan Beaudette Scott Hayes Simon Eching California Department of water Resources Department of land Air and Water ResourcesUniversity of California School of Environment and Energy Shenzhen Graduate SchoolPeking University

The California Simulation of Evapotranspiration of Applied water （CaI-SIMETAw） model is a new tool developed by the California Department of water Resources and the University of California, Davis to perform daily soil water balance and determine crop evapotranspiration （ETo）, evapotranspiration of applied water （ETaw）, and applied water （Aw） for use in California water resources planning. ETaw is a seasonal estimate of the water needed to irrigate a crop assuming 100% irrigation efficiency. The model accounts for soils, crop coefficients, rooting depths, seepage, etc. that influence crop water balance. It provides spatial soil and climate information and it uses historical crop and land-use category information to provide seasonal water balance estimates by combinations of detailed analysis unit and county （DAU/County） over Califomia. The result is a large data base of ETc and ETaw that will be used to update information in the new California water Plan （CwP）. The application uses the daily climate data, i.e., maximum （Tx） and minimum （Tn） temperature and precipitation （Pcp）, which were derived from monthly USDA-NRCS PRISM data （PRISM Group 2011） and daily US National Climate Data Center （NCDC） climate station data to cover California on a 4 kmx4 km change grid spacing. The application uses daily weather data to determine reference evapotranspiration （ETo）, using the Hargreaves-Samani （HS） equation （Hargreaves and Samani 1982, 1985）. Because the HS equation is based on temperature only, ETo from the HS equation were compared with CIMIS ETo at the same locations using available CIMIS data to determine correction factors to estimate CIMIS ETo from the HS ETo to account for spatial climate differences. CaI-SIMETAw also employs near real-time reference evapotranspiration （ETo） information from Spatial CIMIS, which is a model that combines weather station data and remote sensing to provide a grid of ETo information. A second database containing the available soil water

关键词： soil water balance crop water requirements weather generator water resource planning crop coefficient energy use

Petrogenesis, lA-ICP-MS zircon U-Pb geochronology and geodynamic implications of the Kribi metavolcanic rocks,Nyong Group, Congo craton

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Acta Geochimica 2022年第3期41卷 470-495页

作者： Hermine Mvodo Sylvestre Ganno gus Djibril Kouankap Nono Donald Hermann Fossi Philomene Estelle Nga Essomba Marvine Nzepang Tankwa Jean Paul Nzenti Department of Earth Sciences University of YaoundéIP.O.Box 812YaoundeCameroon Department of Geology HTTCUniversity of BamendaP.O.Box 39BambiliBamendaCameroon Institute for Geological and Mining Research P.O.Box 4110YaoundéCameroon Faculty of Mines and Petroleum Industries University of MarouaKaélé08MarouaCameroon

Metavolcanic rocks are well-exposed in the Kribi area within the Nyong Group, Congo craton, but their origin, age, and tectonic significance are poorly *** we report integrated field mapping and petrography,geochemistry, and lA-ICP-MS zircon U-Pb ages of these metavolcanic rocks to constrain their petrogenesis and geodynamic implications. The studied rocks consist of mafic granulite, garnet-amphibole gneiss, and garnet-biotite gneiss, and occur interbanded with sharp contact and intruded by syenite dyke. These metavolcanic rocks are classified as MORB-like tholeiitic to calc-alkaline basalts,basaltic andesite, and rhyodacite rocks with within-plate setting geochemical signatures. The metabasite rocks(basalt to basaltic andesite protolith) are likely the equivalent of a spinel peridotite product representing ~ 2–5 %partial melting of metasomatized mantle source, while the metarhyodacite rocks are derived from the fractional crystallization of the same parental magma. Zircon U-Pb data revealed that the rhyodacite rocks initially formed at2671 ± 51 Ma and underwent later metamorphism at2065 ± 55 Ma. The Neoarchean protolith age is comparable to the ca. 2628 Ma tholeiitic magmatism and ca.2666 Ma high-K granites, suggesting bimodal Neoarchean magmatic event within the Ntem Complex, while the metamorphic ages fall within the ca. 2100–2000 Ma highgrade tectono-metamorphic event attributed to Eburnean/Trans-Amazonian orogeny. At the regional scale,metavolcanic rocks with similar origins and ages are documented in the Sa o Francisco Craton in Brazil, suggesting comparable geodynamic evolution on both sides of the south Atlantic during the Paleoproterozoic.

关键词： Metavolcanic rocks MORB within plate volcanic zone Mantle source Fractional crystallization Congo craton Cameroon