A5049360327- 2D Materials and Applications
- Multiferroics and related materials
- Advanced Condensed Matter Physics
- Advanced Chemical Physics Studies
- Magnetic and transport properties of perovskites and related materials
- Machine Learning in Materials Science
- Catalytic Processes in Materials Science
- Electronic and Structural Properties of Oxides
- Graphene research and applications
- Rare-earth and actinide compounds
- Advancements in Battery Materials
- Iron oxide chemistry and applications
- Catalysis and Oxidation Reactions
- Electron and X-Ray Spectroscopy Techniques
- ZnO doping and properties
- Physics of Superconductivity and Magnetism
- Mesoporous Materials and Catalysis
- Perovskite Materials and Applications
- Solid-state spectroscopy and crystallography
- Inorganic Chemistry and Materials
- Magnetic Properties of Alloys
- Clay minerals and soil interactions
- Topological Materials and Phenomena
- Boron and Carbon Nanomaterials Research
- Quantum, superfluid, helium dynamics
Oak Ridge National Laboratory
2018-2025
Yale University
2020-2023
Massachusetts Institute of Technology
2015-2020
University of Maryland, Baltimore County
2020
Sabancı Üniversitesi
2013
We review recent advances in the capabilities of open source ab initio Quantum Monte Carlo (QMC) package QMCPACK and workflow tool Nexus used for greater efficiency reproducibility. The auxiliary field QMC (AFQMC) implementation has been greatly expanded to include k-point symmetries, tensor-hypercontraction, accelerated graphical processing unit (GPU) support. These scaling memory reductions increase number orbitals that can practically be included AFQMC calculations, increasing accuracy....
Abstract Lack of rigorous reproducibility and validation are significant hurdles for scientific development across many fields. Materials science, in particular, encompasses a variety experimental theoretical approaches that require careful benchmarking. Leaderboard efforts have been developed previously to mitigate these issues. However, comprehensive comparison benchmarking on an integrated platform with multiple data modalities perfect defect materials is still lacking. This work...
Two-dimensional (2D) 1T-VSe2 has prompted significant interest due to the discrepancies regarding alleged ferromagnetism (FM) at room temperature, charge density wave (CDW) states, and interplay between two. We employed a combined Diffusion Monte Carlo (DMC) functional theory (DFT) approach accurately investigate magnetic properties, CDW their responses strain in monolayer 1T-VSe2. Our calculations show delicate competition various phases, revealing critical insights into relationship...
Tricalcium silicate (Ca3SiO5) is heavily used in industry as it the most predominant constituent Portland cement clinkers. In this work, using ab-initio calculations, we assess ability of a large selection substitutions to modify electronic structure M3 polymorph tricalcium silicate. We demonstrate relation between structure, hybridization impurity orbitals, and charge transfer from atoms bulk material. Our work suggests that localization upon introducing impurities can passivate reactive...
Two-dimensional (2D) post-transition metal chalcogenides (PTMCs) have attracted attention due to their suitable bandgaps and lower exciton binding energies, making them more appropriate for electronic, optical, water-splitting devices than graphene monolayer transition dichalcogenides. Of the predicted 2D PTMCs, GaSe has been reliably synthesized experimentally characterized. Despite this fact, quantities such as lattice parameters band character vary significantly depending on which density...
Understanding the behavior of defects in complex oxides is key to controlling myriad ionic and electronic properties these multifunctional materials. The observation defect dynamics, however, requires a unique probe-one sensitive configuration as well its time evolution. Here, we present measurements oxygen vacancy ordering epitaxial thin films SrCoO_{x} brownmillerite-perovskite phase transition employing x-ray photon correlation spectroscopy. These associated synchrotron theory...
We investigate the charge densities, lithium intercalation potentials, and Li-diffusion barrier energies of LixNiO2 (0.0 < x 1.0) system using diffusion quantum Monte Carlo (DMC) method. find an average redox potential 4.1(2) eV a energy 0.39(3) with DMC. Comparisoin densities from DMC density functional theory (DFT) show that local semilocal DFT functionals yield spin polarization incorrect sign on oxygen atoms. The SCAN Hubbard-U correction improves around Ni O atoms, resulting in smaller...
Previous works have controversially claimed near-room-temperature ferromagnetism in two-dimensional (2D) VSe2, with conflicting results throughout the literature. These discrepancies magnetic properties between both phases (T and H) of 2D VSe2 are most likely due to structural parameters being coupled properties. Specifically, a close lattice match similar total energies, which makes it difficult determine phase is observed experimentally. In this study, we used combination density...
We predict that monolayer ${\mathrm{FeCl}}_{2}$ is a two-dimensional piezoelectric ferromagnet (PFM) with easy-axis magnetism and Curie temperature of 260 K. Our ab initio calculations combined data mining reveal 2H-${\mathrm{FeCl}}_{2}$ as the only 2D PFM, its magnetic anisotropy increases many-fold moderate hole doping. develop an analysis based on anisotropies densities explain doping-dependent behavior ${\mathrm{FeCl}}_{2}$, well ${\mathrm{VSe}}_{2}$ ${\mathrm{CrI}}_{3}$, can enable...
High-throughput calculations based on density functional theory (DFT) methods have been widely implemented in the scientific community. However, depending both properties of interest as well particular chemical/structural phase space, accuracy even for correct trends remains a key challenge DFT. In this work, we evaluate use quantum Monte Carlo (QMC) to calculate material formation energies high-throughput environment. We test performance automated QMC 21 compounds with high quality...
We present a many-body diffusion quantum Monte Carlo (DMC) study on the ground- and excited state properties of crystalline CoO polymorphs. To our knowledge, DMC is only electronic structure method available to provide correct energetic ordering within experimental error bars between three polymorphs: rocksalt, wurtzite, zinc blende. compare these results density functional theory (DFT) using state-of-the-art functionals such as SCAN. For structural properties, lattice parameters bulk...
Two-dimensional van der Waals (2D vdW) materials that display ferromagnetism and piezoelectricity have received increased attention. Despite numerous 2D so far been reported as ferromagnetic, developing an air stable transferable vdW material is multiferroic has challenging. To address this problem, we report our work on layered transition metal silicates are derivatives of kaolinites lizardites with substituting Al$^{3+}$ Mg$^{2+}$ sites using ab-initio calculations. Using Density...
Accurate excitation energies of localized defects have been a long-standing problem for electronic structure calculation methods. Using Mn4+-doped solids as our proof principle, we show that diffusion quantum Monte Carlo (DMC) is able to predict phosphorescence emission within statistical error. To demonstrate the generality DMC approach other possible defects, conduct charge density analyses using and functional theory (DFT). We also identify new material with an energy 1.97(8) eV, which...
We present diffusion Monte Carlo (DMC) results for equation of state and quasiparticle gaps manganese binary oxides MnO ${\mathrm{MnO}}_{2}$ the ternary oxide ${\mathrm{LaMnO}}_{3}$. Owing to limited approximations made direct treatment electronic correlations, our DMC-based study correctly describes structural properties such as lattice constant, bulk moduli, cohesive energies. It predicts ground-state phase these oxides, which have different valences. Our demonstrates capability DMC...
Magnetism in lanthanum cobaltite (LCO, LaCoO$_3$) appears to be strongly dependent on strain, defects, and nanostructuring. LCO strontium titanate (STO, SrTiO$_3$) is a ferromagnet with an interesting strain relaxation mechanism that yields lattice modulation. However, the driving force of ferromagnetism still controversial. Experiments debate between vacancy-driven or strain-driven for epitaxial LCO. We found weak lateral modulation superstructure sufficient promote ferromagnetism. find...
Monolayer MnO$_2$ is one of the few predicted two-dimensional (2D) ferromagnets that has been experimentally synthesized and commercially available. The Mermin-Wagner theorem states magnetic order in a 2D material cannot persist unless anisotropy (MA) present perpendicular to plane, which permits finite critical temperature. Previous computational studies have ordering Curie temperature with DFT+U (Density Funtional Theory + Hubbard U correction), results having strong dependence on...
Two-dimensional (2D) 1T-VSe$_2$ has prompted significant interest due to the discrepancies regarding alleged ferromagnetism (FM) at room temperature, charge density wave (CDW) states and interplay between two. We employed a combined Diffusion Monte Carlo (DMC) functional theory (DFT) approach accurately investigate magnetic properties response of strain monolayer 1T-VSe$_2$. Our calculations show delicate competition various phases, revealing critical insights into relationship their...
We investigate the isomerization enthalpy of dihydroazulene/vinylheptafulvene (DHA/VHF) molecular photoswitch system derivatives using electronic structure calculation methods including density functional theory (DFT), quantum Monte Carlo (QMC), and coupled cluster (CCSD(T)). Recent efforts have focused on tuning for solar thermal energy storage applications substitutional groups its five- seven-membered carbon rings, predominantly DFT predictions. However, higher accuracy QMC CCSD(T)...
The study of alloys using computational methods has been a difficult task due to the usually unknown stoichiometry and local atomic ordering different structures experimentally. In order combat this, first-principles have coupled with statistical such as cluster expansion formalism in construct energy hull diagram, which helps determine if an alloyed structure can exist nature. Traditionally, density functional theory (DFT) used workflows. this paper, we propose use chemically accurate...
The intrinsic properties of two-dimensional (2D) SiO2 were revealed by forming the material on inert Au(111). Growth SiO deposition enabled formation a crystalline phase consisting two linked sheets six-membered rings tetrahedral [SiO4] building units. bases tetrahedra form an isostatic 2D kagome lattice. weak interaction with Au allowed new corrugation to be detected: ripples ∼4 nm periodicity that help stabilize layer. On atomic scale, substantial distortions from ideal hexagonal observed...
Lack of rigorous reproducibility and validation are major hurdles for scientific development across many fields. Materials science in particular encompasses a variety experimental theoretical approaches that require careful benchmarking. Leaderboard efforts have been developed previously to mitigate these issues. However, comprehensive comparison benchmarking on an integrated platform with multiple data modalities both perfect defect materials is still lacking. This work introduces...
The properties of [Formula: see text] (M: 3d transition metal) perovskite crystals are significantly dependent on point defects, whether introduced accidentally or intentionally. most studied defects in La-based perovskites the oxygen vacancies and doping impurities La M sites. Here, we identify that intrinsic antisite replacement by metal, M, can be formed under M-rich O-poor growth conditions, based results an accurate many-body ab initio approach. Our fixed-node diffusion Monte Carlo...
Two-dimensional (2D) transition-metal silicates are interesting materials because of their potential ferromagnetism together with inherent piezoelectric response to structural symmetry. Substrate-assisted bottom-up synthesis these offers flexibility in chemical composition. However, synthesizing free-standing layers has been challenging strong overlayer–substrate interactions which hinder exfoliation the overlayer. Here, using density functional theory calculations, we systematically...
Delafossites (ABO 2 ) are a class of layered materials with triangular A and B sub-lattices. Via high-throughput ab initio calculations over wide range delafossites, we identify delafossites that preferentially admit guest species in honeycomb or kagome arrangements to form new ternary compounds.