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153. Tunable Surface Chemistry in Heterogeneous Bilayer Single-Atom Catalysts for Electrocatalytic NOx Reduction to Ammonia

Author

Lv, Xingshuai, Mou, Tong, Li, Jianwei, Kou, Liangzhi, Frauenheim, Thomas, Lv, Xingshuai, Mou, Tong, Li, Jianwei, Kou, Liangzhi, and Frauenheim, Thomas

Abstract

Electrochemical NOx reduction reaction (NOxRR) holds promise for both nitrogen pollution management and low-temperature ammonia (NH3) synthesis; however, it relies on catalysts with controllable reaction pathways and product selectivity. For this purpose, heterogeneous bilayer single-atom catalysts (BSACs) with tunable surface chemistry are proposed as a general design strategy in heterogeneous catalysis. For example, NOxRR on a series of bilayer N-doped graphene (GN) supported single-atom catalysts (denoted as M2–CmNn–GN) are systematically investigated. The BSACs can not only circumvent the undesired metal aggregation and N–N coupling step, but also preserve the advantages of tunable reactivity from a dual-atom site. The intrinsic dipole moment stemming from the asymmetric structure of the heterogeneous BSACs enables enhanced local electric field around reactive sites and allows effective control of chemisorption of reaction species. Interestingly, the polarization-dependent activation of NOx greatly affects the reaction path, limiting potential, and selectivity of the NOxRR. This study highlights a universal strategy for the rational design of catalysts with high performance for NH3 electrosynthesis and beyond.

Published
2022

154. Predicting the Lattice Thermal Conductivity in Nitride Perovskite LaWN3 from ab initio Lattice Dynamics.

Author

Tong, Zhen, Zhang, Yatian, Pecchia, Alessandro, Yam, ChiYung, Zhou, Liujiang, Dumitrică, Traian, and Frauenheim, Thomas

Subjects
LATTICE dynamics, PHONON scattering, THERMAL conductivity, QUANTUM tunneling, NITRIDES, POTENTIAL energy surfaces, RENORMALIZATION (Physics)
Abstract

Using a density functional theory‐based thermal transport model, which includes the effects of temperature (T)‐dependent potential energy surface, lattice thermal expansion, force constant renormalization, and higher‐order quartic phonon scattering processes, it is found that the recently synthesized nitride perovskite LaWN3 displays strong anharmonic lattice dynamics manifested into a low lattice thermal conductivity (κL) and a non‐standard κL∝T−0.491 dependence. At high T, the departure from the standard κL∝T−1 law originates in the dual particle‐wave behavior of the heat carrying phonons, which includes vibrations tied to the N atoms. While the room temperature κL=2.98 W mK‐1 arises mainly from the conventional particle‐like propagation of phonons, there is also a significant atypical wave‐like phonon tunneling effect, leading to a 20% glass‐like heat transport contribution. The phonon broadening effect lowers the particle‐like contribution but increases the glass‐like one. Upon T increase, the glass‐like contribution increases and dominates above T = 850 K. Overall, the low κL with a weak T‐dependence points to a new utility for LaWN3 in energy technology applications, and motivates synthesis and exploration of nitride perovskites. [ABSTRACT FROM AUTHOR]

Published
2023
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165. Optimized hybrid functionals for defect calculations in semiconductors.

Author

Deák, Peter, Lorke, Michael, Aradi, Bálint, and Frauenheim, Thomas

Subjects
FUNCTIONALS, CRYSTAL optics, DENSITY functional theory, SEMICONDUCTORS
Abstract

Defects influence the electronic and optical properties of crystals, so their identification is crucial to develop device technology for materials of micro-/optoelectronics and photovoltaics. The identification requires the accurate calculation of the electronic transitions and the paramagnetic properties of defects. The achievable accuracy is strongly limited in the case of the (semi)local approximations to density functional theory, because of the underestimation of the gap and of the degree of localization. In the past two decades, hybrid functionals, mixing semilocal and nonlocal exchange semiempirically, have emerged as an alternative. Very often, however, the parameters of such hybrids have to be tuned from material to material. In this paper, we describe the theoretical foundations for the proper tuning and show that if the relative positions of the band edge states are well reproduced, and the generalized Koopmans's theorem is fulfilled by the given parameterization, the calculated defect levels and localizations can be very accurate. As demonstrated here, this can be achieved with the two-parameter Heydt-Scuseria-Ernzerhof hybrid, HSE(α,μ) for diamond, Si, Ge, TiO2, GaAs, CuGaS(Se)2, GaSe, GaN, and Ga2O3. The paper describes details of the parameterization process and discusses the limitations of optimizing HSE functionals. Based on the gained experience, future directions for improving exchange functionals are also provided. [ABSTRACT FROM AUTHOR]

Published
2019
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167. Plasmon-Enhanced Exciton Delocalization in Squaraine-Type Molecular Aggregates

Author

Quenzel, Thomas, primary, Timmer, Daniel, additional, Gittinger, Moritz, additional, Zablocki, Jennifer, additional, Zheng, Fulu, additional, Schiek, Manuela, additional, Lützen, Arne, additional, Frauenheim, Thomas, additional, Tretiak, Sergei, additional, Silies, Martin, additional, Zhong, Jin-Hui, additional, De Sio, Antonietta, additional, and Lienau, Christoph, additional

Published
2022
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174. DFT exchange: sharing perspectives on the workhorse of quantum chemistry and materials science

Author

Teale, Andrew M., primary, Helgaker, Trygve, additional, Savin, Andreas, additional, Adamo, Carlo, additional, Aradi, Bálint, additional, Arbuznikov, Alexei V., additional, Ayers, Paul W., additional, Baerends, Evert Jan, additional, Barone, Vincenzo, additional, Calaminici, Patrizia, additional, Cancès, Eric, additional, Carter, Emily A., additional, Chattaraj, Pratim Kumar, additional, Chermette, Henry, additional, Ciofini, Ilaria, additional, Crawford, T. Daniel, additional, De Proft, Frank, additional, Dobson, John F., additional, Draxl, Claudia, additional, Frauenheim, Thomas, additional, Fromager, Emmanuel, additional, Fuentealba, Patricio, additional, Gagliardi, Laura, additional, Galli, Giulia, additional, Gao, Jiali, additional, Geerlings, Paul, additional, Gidopoulos, Nikitas, additional, Gill, Peter M. W., additional, Gori-Giorgi, Paola, additional, Görling, Andreas, additional, Gould, Tim, additional, Grimme, Stefan, additional, Gritsenko, Oleg, additional, Jensen, Hans Jørgen Aagaard, additional, Johnson, Erin R., additional, Jones, Robert O., additional, Kaupp, Martin, additional, Köster, Andreas M., additional, Kronik, Leeor, additional, Krylov, Anna I., additional, Kvaal, Simen, additional, Laestadius, Andre, additional, Levy, Mel, additional, Lewin, Mathieu, additional, Liu, Shubin, additional, Loos, Pierre-François, additional, Maitra, Neepa T., additional, Neese, Frank, additional, Perdew, John P., additional, Pernal, Katarzyna, additional, Pernot, Pascal, additional, Piecuch, Piotr, additional, Rebolini, Elisa, additional, Reining, Lucia, additional, Romaniello, Pina, additional, Ruzsinszky, Adrienn, additional, Salahub, Dennis R., additional, Scheffler, Matthias, additional, Schwerdtfeger, Peter, additional, Staroverov, Viktor N., additional, Sun, Jianwei, additional, Tellgren, Erik, additional, Tozer, David J., additional, Trickey, Samuel B., additional, Ullrich, Carsten A., additional, Vela, Alberto, additional, Vignale, Giovanni, additional, Wesolowski, Tomasz A., additional, Xu, Xin, additional, and Yang, Weitao, additional

Published
2022
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180. Artificial Intelligence Designer for Highly-Efficient Organic Photovoltaic Materials

Author

Sun, Wenbo, primary, Zheng, Yujie, additional, Zhang, Qi, additional, Yang, Ke, additional, Chen, Haiyan, additional, Cho, Yongjoon, additional, Fu, Jiehao, additional, Odunmbaku, Omololu, additional, Shah, Akeel A., additional, Xiao, Zeyun, additional, Lu, Shirong, additional, Chen, Shanshan, additional, Li, Meng, additional, Qin, Bo, additional, Yang, Changduk, additional, Frauenheim, Thomas, additional, and Sun, Kuan, additional

Published
2021
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196. Hydroxyl-Boosted Nitrogen Reduction Reaction : The Essential Role of Surface Hydrogen in Functionalized MXenes

Author

Lv, Xingshuai, Kou, Liangzhi, Frauenheim, Thomas, Lv, Xingshuai, Kou, Liangzhi, and Frauenheim, Thomas

Abstract

MXenes, an emerging family of two-dimensional (2D) metal carbides and nitrides, have been demonstrated to be effective nitrogen reduction reaction (NRR) catalysts. So far, most of the theoretical studies toward NRR are based on bare MXenes; however, the structural stabilities are questionable. In this work, we studied the NRR process on several synthesized MXenes (Ti2C, V2C, Cr2C, Zr2C, Nb2C, Mo2C, Hf2C, and Ta2C) with hydroxyl (OH) termination since the structures are preferred under NRR operating conditions as per Pourbaix stability diagrams. It is found that OH plays an essential role in tuning the NRR chemistry, as a new surface-hydroxylation mechanism. Different from the widely accepted NRR mechanism where only protons are involved in the reaction, hydrogen (H) atoms from surface hydroxyl could be captured by the intermediate and participate into the NRR, while the remaining H vacancy can subsequently be self-repaired by the protons under the applied potential. The cooperative effect of surface hydroxylation can effectively boost the NRR, while Mo2C(OH)2 stands out with the most favorable limiting potential of -0.62 V and highest selectivity. Moreover, new scaling relationships based on the H vacancy energy are established, elucidating the possibility for structure-activity tuning. This study not only elaborates the essential role of surface OH functionalization in evaluating NRR performance but also affords new insights into advance sustainable NH3 production.

Published
2021

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