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Hubbard U through polaronic defect states

npj Computational Materials 2022年第1期8卷 2504-2511页

作者： Stefano Falletta alf.ed. pasquarello Chaire de Simulationàl’Echelle Atomique(CSEA) Ecole Polytechnique Fédérale de Lausanne(EPFL)CH-1015LausanneSwitzerland

Since the preliminary work of Anisimov and co-workers,the Hubbard corrected DFT+U functional has been used for predicting properties of correlated materials by applying on-site effective Coulomb interactions to specific ***,the determination of the Hubbard U parameter has remained under intense discussion despite the multitude of approaches ***,we define a selection criterion based on the use of polaronic defect states for the enforcement of the piecewise linearity of the total energy upon electron occupation.A good agreement with results from piecewise linear hybrid functionals is found for the electronic and structural properties of polarons,including the formation *** values of U determined in this way are found to give a robust description of the polaron energetics upon variation of the considered *** particular,we also address a polaron hopping pathway,finding that the determined value of U leads to accurate energetics without requiring a configurational-dependent *** is emphasized that the selection of U should be based on physical properties directly associated with the orbitals to which U is applied,rather than on more global properties such as band gaps and band *** comparison,we also determine U through a well-established linear-response scheme finding noticeably different values of U and consequently different formation *** origins of these discrepancies are *** case studies,we consider the self-trapped electron in BiVO_(4),the self-trapped hole in MgO,the Li-trapped hole in MgO,and the Al-trapped hole inα-SiO_(2).

关键词： Hubbard polaron piecewise

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Range-separated hybrid functionals for accurate prediction of band gaps of extended systems

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npj Computational Materials 2023年第1期9卷 1237-1245页

作者： Jing Yang Stefano Falletta alf.ed. pasquarello Chaire de Simulationàl’Echelle Atomique(CSEA) Ecole Polytechnique Fédérale de Lausanne(EPFL)Lausanne CH-1015Switzerland

In this work,we systematically evaluate the accuracy in band gap prediction of range-separated hybrid functionals on a large set of semiconducting and insulating materials and carry out comparisons with the performance of their global *** observe that all the range-separated hybrid functionals that correctly describe the long-range dielectric screening significantly improve upon standard hybrid functionals such as PBE0 and *** choice of the short-range Fock exchange fraction and the screening length can further reduce the predicted *** then propose a universal expression for the selection of the inverse screening parameter as a function of the short-range and long-range Fock exchange fractions,which results in a mean absolute error as small as 0.15 eV for band gap prediction.

关键词： separated functionals exchange

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Accurate and efficient band-gap predictions for metal halide perovskites at finite temperature

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npj Computational Materials 2022年第1期8卷 2267-2279页

作者： Haiyuan Wang Alexey Tal Thomas Bischoff Patrick Gono alf.ed. pasquarello Chaire de Simulationàl’Echelle Atomique(CSEA) Ecole Polytechnique Fédérale de Lausanne(EPFL)LausanneCH-1015Switzerland

We develop a computationally efficient scheme to accurately determine finite-temperature band gaps for metal halide perovskites belonging to the class ABX_(3)(A=Rb,Cs;B=Ge,Sn,Pb;and X=F,Cl,Br,I).First,an initial estimate of the band gap is provided for the ideal crystalline structure through the use of a range-separated hybrid functional,in which the parameters are determined non-empirically from the electron density and the high-frequency dielectric ***,we consider two kinds of band-gap corrections to account for spin-orbit coupling and thermal vibrations including zero-point *** particular,the latter effect is accounted for through the special displacement method,which consists in using a single distorted configuration obtained from the vibrational frequencies and eigenmodes,thereby avoiding lengthy molecular *** sequential consideration of both corrections systematically improves the band gaps,reaching a mean absolute error of 0.17 eV with respect to experimental *** computational efficiency of our scheme stems from the fact that only a single calculation at the hybrid-functional level is required and that it is sufficient to evaluate the corrections at the semilocal level of *** scheme is thus convenient for the screening of large databases of metal halide perovskites,including large-size systems.

关键词： theory. perovskite halide

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Absolute band alignment at semiconductor-water interfaces using explicit and implicit descriptions for liquid water

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npj Computational Materials 2019年第1期5卷 256-261页

作者： Nicolas G.Hörmann Zhendong Guo Francesco Ambrosio Oliviero Andreussi alf.ed. pasquarello Nicola Marzari Theory and Simulation of Materials(THEOS) and National Centre for Computational Design and Discovery of Novel Materials(MARVEL)École Polytechnique Fédérale de Lausanne1015 LausanneSwitzerland Chair of Theoretical Chemistry Technische Universität München85748 GarchingGermany Chaire de Simulationàl’Echelle Atomique(CSEA) École Polytechnique Fédérale de Lausanne1015 LausanneSwitzerland Department of Physics University of North TexasDentonTX 76207USA

Quantum mechanical simulations that include the effects of the liquid environment are highly relevant for the characterization of solid-liquid interfaces,which is crucial for the design of a wide range of *** this work we present a rigorous and systematic study of the band alignment of semiconductors in aqueous solutions by contrasting a range of hybrid explicit/implicit models against explicit atomistic simulations based on density-functional *** find that consistent results are obtained provided that the first solvation shell is treated ***,the first molecular layer of explicit water is only relevant for the pristine surfaces without dissociatively adsorbed water,hinting at the importance of saturating the surface with quantum mechanical *** referencing the averaged electrostatic potentials of explicit and implicit water against vacuum,we provide absolute alignments,finding maximal differences of only~0.1–0.2 ***,the implicit reference potential is shown to exhibit an intrinsic offset of−0.33 V with respect to vacuum,which is traced back to the absence of an explicit water surface in the implicit *** results pave the way for accurate simulations of solid-liquid interfaces using minimalistic explicit/implicit models.

关键词： theory implicit explicit

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