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Stefano Baroni - One of the best experts on this subject based on the ideXlab platform.

  • turbo Charging Time dependent density functional theory with lanczos chains
    Journal of Chemical Physics, 2008
    Co-Authors: Dario Rocca, Ralph Gebauer, Yousef Saad, Stefano Baroni
    Abstract:

    We introduce a new implementation of Time-dependent density-functional theory which allows the entire spectrum of a molecule or extended system to be computed with a numerical effort comparable to that of a single standard ground-state calculation. This method is particularly well suited for large systems and/or large basis sets, such as plane waves or real-space grids. By using a superoperator formulation of linearized Time-dependent density-functional theory, we first represent the dynamical polarizability of an interacting-electron system as an off-diagonal matrix element of the resolvent of the Liouvillian superoperator. One-electron operators and density matrices are treated using a representation borrowed from Time-independent density-functional perturbation theory, which permits us to avoid the calculation of unoccupied Kohn–Sham orbitals. The resolvent of the Liouvillian is evaluated through a newly developed algorithm based on the nonsymmetric Lanczos method. Each step of the Lanczos recursion es...

  • Turbo Charging Time-dependent density-functional theory with Lanczos chains
    Journal of Chemical Physics, 2008
    Co-Authors: Dario Rocca, Erik Van Sebille, Ralph Gebauer, Yousef Saad, Stefano Baroni
    Abstract:

    We introduce a new implementation of Time-dependent density-functional theory which allows the entire spectrum of a molecule or extended system to be computed with a numerical effort comparable to that of a single standard ground-state calculation. This method is particularly well suited for large systems and/or large basis sets, such as plane waves or real-space grids. By using a superoperator formulation of linearized Time-dependent density-functional theory, we first represent the dynamical polarizability of an interacting-electron system as an off-diagonal matrix element of the resolvent of the Liouvillian superoperator. One-electron operators and density matrices are treated using a representation borrowed from Time-independent density-functional perturbation theory, which permits us to avoid the calculation of unoccupied Kohn-Sham orbitals. The resolvent of the Liouvillian is evaluated through a newly developed algorithm based on the nonsymmetric Lanczos method. Each step of the Lanczos recursion essentially requires twice as many operations as a single step of the iterative diagonalization of the unperturbed Kohn-Sham Hamiltonian. Suitable extrapolation of the Lanczos coefficients allows for a dramatic reduction of the number of Lanczos steps necessary to obtain well converged spectra, bringing such number down to hundreds (or a few thousands, at worst) in typical plane-wave pseudopotential applications. The resulting numerical workload is only a few Times larger than that needed by a ground-state Kohn-Sham calculation for a same system. Our method is demonstrated with the calculation of the spectra of benzene, C(60) fullerene, and of chlorophyll a.

Dario Rocca - One of the best experts on this subject based on the ideXlab platform.

  • turbo Charging Time dependent density functional theory with lanczos chains
    Journal of Chemical Physics, 2008
    Co-Authors: Dario Rocca, Ralph Gebauer, Yousef Saad, Stefano Baroni
    Abstract:

    We introduce a new implementation of Time-dependent density-functional theory which allows the entire spectrum of a molecule or extended system to be computed with a numerical effort comparable to that of a single standard ground-state calculation. This method is particularly well suited for large systems and/or large basis sets, such as plane waves or real-space grids. By using a superoperator formulation of linearized Time-dependent density-functional theory, we first represent the dynamical polarizability of an interacting-electron system as an off-diagonal matrix element of the resolvent of the Liouvillian superoperator. One-electron operators and density matrices are treated using a representation borrowed from Time-independent density-functional perturbation theory, which permits us to avoid the calculation of unoccupied Kohn–Sham orbitals. The resolvent of the Liouvillian is evaluated through a newly developed algorithm based on the nonsymmetric Lanczos method. Each step of the Lanczos recursion es...

  • Turbo Charging Time-dependent density-functional theory with Lanczos chains
    Journal of Chemical Physics, 2008
    Co-Authors: Dario Rocca, Erik Van Sebille, Ralph Gebauer, Yousef Saad, Stefano Baroni
    Abstract:

    We introduce a new implementation of Time-dependent density-functional theory which allows the entire spectrum of a molecule or extended system to be computed with a numerical effort comparable to that of a single standard ground-state calculation. This method is particularly well suited for large systems and/or large basis sets, such as plane waves or real-space grids. By using a superoperator formulation of linearized Time-dependent density-functional theory, we first represent the dynamical polarizability of an interacting-electron system as an off-diagonal matrix element of the resolvent of the Liouvillian superoperator. One-electron operators and density matrices are treated using a representation borrowed from Time-independent density-functional perturbation theory, which permits us to avoid the calculation of unoccupied Kohn-Sham orbitals. The resolvent of the Liouvillian is evaluated through a newly developed algorithm based on the nonsymmetric Lanczos method. Each step of the Lanczos recursion essentially requires twice as many operations as a single step of the iterative diagonalization of the unperturbed Kohn-Sham Hamiltonian. Suitable extrapolation of the Lanczos coefficients allows for a dramatic reduction of the number of Lanczos steps necessary to obtain well converged spectra, bringing such number down to hundreds (or a few thousands, at worst) in typical plane-wave pseudopotential applications. The resulting numerical workload is only a few Times larger than that needed by a ground-state Kohn-Sham calculation for a same system. Our method is demonstrated with the calculation of the spectra of benzene, C(60) fullerene, and of chlorophyll a.

Yousef Saad - One of the best experts on this subject based on the ideXlab platform.

  • turbo Charging Time dependent density functional theory with lanczos chains
    Journal of Chemical Physics, 2008
    Co-Authors: Dario Rocca, Ralph Gebauer, Yousef Saad, Stefano Baroni
    Abstract:

    We introduce a new implementation of Time-dependent density-functional theory which allows the entire spectrum of a molecule or extended system to be computed with a numerical effort comparable to that of a single standard ground-state calculation. This method is particularly well suited for large systems and/or large basis sets, such as plane waves or real-space grids. By using a superoperator formulation of linearized Time-dependent density-functional theory, we first represent the dynamical polarizability of an interacting-electron system as an off-diagonal matrix element of the resolvent of the Liouvillian superoperator. One-electron operators and density matrices are treated using a representation borrowed from Time-independent density-functional perturbation theory, which permits us to avoid the calculation of unoccupied Kohn–Sham orbitals. The resolvent of the Liouvillian is evaluated through a newly developed algorithm based on the nonsymmetric Lanczos method. Each step of the Lanczos recursion es...

  • Turbo Charging Time-dependent density-functional theory with Lanczos chains
    Journal of Chemical Physics, 2008
    Co-Authors: Dario Rocca, Erik Van Sebille, Ralph Gebauer, Yousef Saad, Stefano Baroni
    Abstract:

    We introduce a new implementation of Time-dependent density-functional theory which allows the entire spectrum of a molecule or extended system to be computed with a numerical effort comparable to that of a single standard ground-state calculation. This method is particularly well suited for large systems and/or large basis sets, such as plane waves or real-space grids. By using a superoperator formulation of linearized Time-dependent density-functional theory, we first represent the dynamical polarizability of an interacting-electron system as an off-diagonal matrix element of the resolvent of the Liouvillian superoperator. One-electron operators and density matrices are treated using a representation borrowed from Time-independent density-functional perturbation theory, which permits us to avoid the calculation of unoccupied Kohn-Sham orbitals. The resolvent of the Liouvillian is evaluated through a newly developed algorithm based on the nonsymmetric Lanczos method. Each step of the Lanczos recursion essentially requires twice as many operations as a single step of the iterative diagonalization of the unperturbed Kohn-Sham Hamiltonian. Suitable extrapolation of the Lanczos coefficients allows for a dramatic reduction of the number of Lanczos steps necessary to obtain well converged spectra, bringing such number down to hundreds (or a few thousands, at worst) in typical plane-wave pseudopotential applications. The resulting numerical workload is only a few Times larger than that needed by a ground-state Kohn-Sham calculation for a same system. Our method is demonstrated with the calculation of the spectra of benzene, C(60) fullerene, and of chlorophyll a.

Ralph Gebauer - One of the best experts on this subject based on the ideXlab platform.

  • turbo Charging Time dependent density functional theory with lanczos chains
    Journal of Chemical Physics, 2008
    Co-Authors: Dario Rocca, Ralph Gebauer, Yousef Saad, Stefano Baroni
    Abstract:

    We introduce a new implementation of Time-dependent density-functional theory which allows the entire spectrum of a molecule or extended system to be computed with a numerical effort comparable to that of a single standard ground-state calculation. This method is particularly well suited for large systems and/or large basis sets, such as plane waves or real-space grids. By using a superoperator formulation of linearized Time-dependent density-functional theory, we first represent the dynamical polarizability of an interacting-electron system as an off-diagonal matrix element of the resolvent of the Liouvillian superoperator. One-electron operators and density matrices are treated using a representation borrowed from Time-independent density-functional perturbation theory, which permits us to avoid the calculation of unoccupied Kohn–Sham orbitals. The resolvent of the Liouvillian is evaluated through a newly developed algorithm based on the nonsymmetric Lanczos method. Each step of the Lanczos recursion es...

  • Turbo Charging Time-dependent density-functional theory with Lanczos chains
    Journal of Chemical Physics, 2008
    Co-Authors: Dario Rocca, Erik Van Sebille, Ralph Gebauer, Yousef Saad, Stefano Baroni
    Abstract:

    We introduce a new implementation of Time-dependent density-functional theory which allows the entire spectrum of a molecule or extended system to be computed with a numerical effort comparable to that of a single standard ground-state calculation. This method is particularly well suited for large systems and/or large basis sets, such as plane waves or real-space grids. By using a superoperator formulation of linearized Time-dependent density-functional theory, we first represent the dynamical polarizability of an interacting-electron system as an off-diagonal matrix element of the resolvent of the Liouvillian superoperator. One-electron operators and density matrices are treated using a representation borrowed from Time-independent density-functional perturbation theory, which permits us to avoid the calculation of unoccupied Kohn-Sham orbitals. The resolvent of the Liouvillian is evaluated through a newly developed algorithm based on the nonsymmetric Lanczos method. Each step of the Lanczos recursion essentially requires twice as many operations as a single step of the iterative diagonalization of the unperturbed Kohn-Sham Hamiltonian. Suitable extrapolation of the Lanczos coefficients allows for a dramatic reduction of the number of Lanczos steps necessary to obtain well converged spectra, bringing such number down to hundreds (or a few thousands, at worst) in typical plane-wave pseudopotential applications. The resulting numerical workload is only a few Times larger than that needed by a ground-state Kohn-Sham calculation for a same system. Our method is demonstrated with the calculation of the spectra of benzene, C(60) fullerene, and of chlorophyll a.

Xiaosong Hu - One of the best experts on this subject based on the ideXlab platform.

  • Charging optimization in lithium-ion batteries based on temperature rise and charge Time
    Applied Energy, 2017
    Co-Authors: Caiping Zhang, Qiujiang Liu, Yang Gao, Weige Zhang, Jiuchun Jiang, Xiaosong Hu
    Abstract:

    Abstract Lithium-ion battery fast Charging issues have become a main bottleneck of large-scale deployment of electric vehicles. This paper develops a polarization based Charging Time and temperature rise optimization strategy for lithium-ion batteries. An enhanced thermal behavior model is introduced to improve the solution accuracy at high Charging current, in which the relationship between polarization voltage and charge current is addressed. Genetic algorithm (GA) is employed to search for the optimal Charging current trajectories. The effects of weighting coefficients of Charging Time and temperature rise on battery Charging performance are discussed. The Charging Time of the optimized Charging protocol is reduced by 50%, and the associated temperature rise is almost identical, compared to 1/3C constant current-constant voltage (CC-CV) Charging. Aging experiments demonstrate that the proposed Charging method has a similar capacity retention ratio to that of 0.5 CC-CV Charging after 700 cycles, thereby accomplishing a good balance between Charging speed and lifeTime.

  • Polarization Based Charging Time and Temperature Rise Optimization for Lithium-ion Batteries☆
    Energy Procedia, 2016
    Co-Authors: Caiping Zhang, Weige Zhang, Jiuchun Jiang, Xiaosong Hu
    Abstract:

    Abstract The Lithium-ion battery fast Charging issues have become the bottleneck of its application as rapid development of electric vehicles. This paper developed a polarization based Charging Time and temperature rise optimization strategy for lithium-ion batteries. The enhanced thermal behavior model is introduced to improve the accuracy at high Charging current, in which the relationship between the polarization voltage and charge current is addressed. Genetic algorithm (GA) is employed to search for the optimal Charging current trajectories. The effects of Charging Time and temperature rise weight coefficients on battery Charging performance is discussed. The Charging Time of the optimized Charging pattern is reduced by 50%, and the temperature rise is almost identical compared to 1/3C constant current-constant voltage (CC-CV) Charging pattern, balancing the battery life and Charging speed.

  • Charging Time and loss optimization for linmc and lifepo4 batteries based on equivalent circuit models
    Journal of Power Sources, 2013
    Co-Authors: Xiaosong Hu, Shengbo Li, Huei Peng
    Abstract:

    Battery management system monitors and mitigates the operation of battery cells and stacks and is important for battery safety and reliability. This paper presents a dual-objective optimal Charging strategy for two types of Li-ion batteries, which considers the conflict objectives of Charging Time and Charging loss. The battery models developed in a prior research are used in the Charging optimization. The influences of the Charging voltage threshold, temperature, and health status on the Charging results are analyzed for both lithium nickelemanganeseecobalt oxide (LiNMC) and lithium iron phosphate (LiFePO4) batteries. A comparison with the Charging results based on the models that cannot describe the entire battery dynamics is also performed.

  • Optimal multistage Charging of NCA/graphite lithium-ion batteries based on electro-thermal-aging dynamics
    IEEE Transactions on Transportation Electrification, 1
    Co-Authors: Xiaosong Hu, Yusheng Zheng
    Abstract:

    Lithium-ion (Li-ion) batteries have been extensively used in electric vehicles, portable electronics, cell phones, and laptops. The Charging protocol, as one of the most critical technologies for Li-ion battery systems, has a significant impact on battery performance. Charging current affects battery degradation and Charging Time, and therefore, it needs to be carefully optimized. To this end, a novel Charging protocol using a series of constant Charging currents has been developed, which considers the Charging Time and the battery capacity fade simultaneously. These two conflicting Charging objectives are traded off by solving a multi-objective optimization problem based on battery electro-thermal-aging behavior. Particle swarm optimization (PSO) has been applied to obtain the optimal Charging current profile. Three optimal Charging strategies for minimum Charging Time, minimum battery aging, and balanced Charging performance are obtained by changing the weight factor. The proposed balanced Charging is capable of reducing the Charging Time significantly with a negligible increase in capacity degradation compared to the 0.5C CC-CV strategy recommended by the manufacturer.