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Hubbard U through polaronic defect states

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

作者： Stefano falletta Alfredo 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

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 Alfredo 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

Ion beam etching redeposition for 3d multimaterial nanostructure manufacturing

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Microsystems & Nanoengineering 2019年第1期5卷 515-522页

作者： B.X.E.desbiolles A.Bertsch P.Renaud Laboratory of Microsystems LMIS4 Ecole Polytechnique Fédérale de Lausanne(EPFL)LausanneSwitzerland

A novel fabrication method based on the local sputtering of photoresist sidewalls during ion beam etching is *** method allows for the manufacture of three-dimensional multimaterial nanostructures at the wafer scale in only four process *** of various shapes and profiles can be fabricated at sub-100-nm dimensions with unprecedented freedom in material *** nanostructures such as nanochannels,multimaterial nanowalls,and suspended networks were successfully fabricated using only standard microprocessing *** provides an alternative to traditional nanofabrication techniques,as well as new opportunities for biosensing,nanofluidics,nanophotonics,and nanoelectronics.

关键词： walls beam steps

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 Alfredo 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

Modelling and mathematical results arising from ferromagnetic problems

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Science China Mathematics 2012年第5期55卷 1053-1067页

作者： deSCLOUX Jean fLUECK Michel RAPPAZ Jacques department of Mathematics Ecole Polytechnique Fdrale de Lausanne (EPFL)Lausanne 1015Switzerland

Abstract In this article, we investigate the equations of magnetostaties for a configuration where a ferromagnetic material occupies a bounded domain and is surrounded by vacuum. furthermore, the ferromagnetic law takes the form B=μ0μr（｜H｜）Hi i.e., the magnetizing field H and the magnetic induction B are collinear, but the relative permeability μr is allowed to depend on the modulus of H. We prove the well-posedness of the magnetostatic problem under suitable convexity assumptions, and the convergence of several iterative methods, both for the original problem set in the Beppo-Levi space W1（R3）, and for a finite-dimensional approximation. The theoretical results are illustrated by numerical examples, which capture the known physical phenomena.

关键词： ferromagnetism nonlinear elliptic problems finite element methods optimisation algorithms

维普期刊数据库

Microfluidics-enabled phenotyping of a whole population of *** worms over their embryonic and post-embryonic development at single-organism resolution

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Microsystems & Nanoengineering 2018年第1期4卷 345-355页

作者： Maria Cristina Letizia Matteo Cornaglia Raphaël Trouillon Vincenzo Sorrentino Laurent Mouchiroud Maroun S.Bou Sleiman Johan Auwerx Martin A.M.Gijs ecole polytechnique fédérale de lausanne Laboratory of MicrosystemsLausanneSwitzerland ecole polytechnique fédérale de lausanne Laboratory of Integrative Systems PhysiologyLausanneSwitzerland

The organism Caenorhabditis elegans is a performant model system for studying human biological processes and diseases,but until now all phenome data are produced as population-averaged *** of individual responses to drug treatments would however be more ***,a new strategy to track different phenotypic traits of individual *** nematodes throughout their full life-cycle-i.e.,embryonic and post-embryonic development,until adulthood onset,differently from life-span-is *** an automated fashion,single worms were synchronized,isolated,and cultured from egg to adulthood in a microfluidic device,where their identity was preserved during their whole *** phenotypes were monitored and quantified for each animal,resulting in high-content phenome ***,the method was validated by analyzing the response of *** to doxycycline,an antibiotic fairly well-known to prolong the development and activate mitochondrial stress-response pathways in different ***,the obtained extensive single-worm phenome not only confirmed the dramatic doxycycline effect on the worm developmental delay,but more importantly revealed subtle yet severe treatment-dependent phenotypes that are representative of minority subgroups and would have otherwise stayed hidden in an averaged *** heterogeneous response started during the embryonic development,which makes essential having a dedicated chip that allows including this early developmental stage in the drug *** approach would therefore allow elucidating pharmaceutical or therapeutic responses that so far were still being overlooked.

关键词： fluid treatment otherwise

Harboring CAR-T cells using an injectable scaffold to treat solid tumors

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National Science Review 2024年第5期11卷 91-92页

作者： Li Tang Institute of Bioengineering (IBI) école polytechnique fédérale de Lausanne (EPFL)

Genetic expression of chimeric antigen receptors (CAR) enables T cells to target and kill cancer cells in an MHCindependent manner, resulting in a potent antitumor response [1]. To date, more than 10 CAR-T cell products have been approved globally for the treatment of hematologic disorders such as relapsed/refractory B-cell acute lymphoblastic leukemia, non-Hodgkin lymphoma, and multiple myeloma [2,3].

关键词： scaffold cells solid treat harboring injectable tumors using

Two-phase air-water flows: Scale effects in physical modeling

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Journal of Hydrodynamics 2014年第2期26卷 291-298页

作者： PfISTER Michael CHANSON Hubert ecole polytechnique fédérale de lausanne (epfl) Laboratory of Hydraulic Constructions (LCH) The University of Queensland School of Civil Engineering

Physical modeling represents probably the oldest design tool in hydraulic engineering together with analytical approaches. In free surface flows, the similitude based upon a froude similarity allows for a correct representation of the dominant forces, namely gravity and inertia. As a result fluid flow properties such as the capillary forces and the viscous forces might be incorrectly reproduced, affecting the air entrainment and transport capacity of a high-speed model flow. Small physical models operating under a froude similitude systematically underestimate the air entrainment rate and air-water interfacial properties. To limit scale effects, minimal values of Reynolds or Weber number have to be respected. The present article summarizes the physical background of such limitations and their combination in terms of the Morton number. Based upon a literature review, the existing limits are presented and discussed, resulting in a series of more conservative recommendations in terms of air concentration scaling. for other air-water flow parameters, the selection of the criteria to assess scale effects is critical because some parameters （e.g., bubble sizes, turbulent scales） can be affected by scale effects, even in relatively large laboratory models.

关键词： air entrainment hydraulic structures physical modeling scale effects two-phase flow Morton number

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Self-referenced photonic chip soliton Kerr frequency comb

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Light(Science & Applications) 2016年第1期5卷 282-287页

作者： Victor Brasch Erwan Lucas John d Jost Michael Geiselmann Tobias J Kippenberg École polytechnique fédérale de lausanne(epfl)–IPHYS Lausanne CH-1015Switzerland

Self-referencing turns pulsed laser systems into self-referenced frequency *** frequency combs allow counting of optical frequencies and have a wide range of *** required optical bandwidth to implement self-referencing is typically obtained via nonlinear broadening in optical *** advances in the field of Kerr frequency combs have provided a path toward the development of compact frequency comb sources that provide broadband frequency combs,exhibit microwave repetition rates and are compatible with on-chip photonic *** devices have the potential to significantly expand the use of frequency *** to date,self-referencing of such Kerr frequency combs has only been attained by applying conventional,fiber-based broadening *** we demonstrate external broadening-free self-referencing of a Kerr frequency *** optical spectrum spanning two-thirds of an octave is directly synthesized from a continuous wave laser-driven silicon nitride microresonator using temporal dissipative Kerr soliton formation and soliton Cherenkov *** this coherent bandwidth and two continuous wave transfer lasers in a 2f–3f self-referencing scheme,we are able to detect the offset frequency of the soliton Kerr frequency *** stabilizing the repetition rate to a radio frequency reference,the self-referenced frequency comb is used to count and track the continuous wave pump laser’s *** work demonstrates the principal ability of soliton Kerr frequency combs to provide microwave-to-optical clockworks on a chip.

关键词： frequency combs integrated optics Kerr frequency combs metrology microresonator frequency combs nonlinear optics