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A rational expansion of the Fermi density operator is proposed. This approach allows to calculate efficiently physical properties of fermionic systems at finite temperatures without solving an eigenvalue problem. Using N evaluations of the…

Computational Physics · Physics 2009-10-30 F. Gagel

We present several finite-temperature recursive Fermi-operator expansion schemes based on the second-order spectral projection (SP2) method. Our approach builds on a previous observation that the electronic structure problem, as formulated…

In a recent paper we have suggested that the finite temperature density matrix can be computed efficiently by a combination of polynomial expansion and iterative inversion techniques. We present here significant improvements over this…

Materials Science · Physics 2010-10-19 Michele Ceriotti , Thomas D. Kühne , Michele Parrinello

In order to study structure of the crust in neutron stars, we develop a finite-temperature Skyrme-Hartree-Fock method in the full three-dimensional coordinate space using the Fermion operator expansion method. It provides us with a possible…

Nuclear Theory · Physics 2023-03-02 Takashi Nakatsukasa

A nuclear density functional can be used to find the binding energy and shell structure of nuclei and the energy gap in superconducting nuclear matter. In this paper, we study the possible application of a nuclear density functional theory…

Nuclear Theory · Physics 2011-04-08 Yeunhwan Lim

The prediction of cross sections for nuclei far off stability is crucial in the field of nuclear astrophysics. In recent calculations the nuclear level density -- as an important ingredient to the statistical model (Hauser-Feshbach) -- has…

Astrophysics · Physics 2016-08-30 T. Rauscher , F. -K. Thielemann , K. -L. Kratz

A new formalism, called "tensor optimized Fermi sphere (TOFS) method", is developed to treat the nuclear matter using a bare interaction among nucleons. In this method, the correlated nuclear matter wave function is taken to be a power…

Nuclear Theory · Physics 2019-02-12 Taiichi Yamada

In the framework of the KIDS generalized energy density functional (EDF), the nuclear equation of state (EoS) is expressed as an expansion in powers of the Fermi momentum or the cubic root of the density ($\rho^{1/3}$). Although an optimal…

Nuclear Theory · Physics 2019-07-24 Hana Gil , Young-Min Kim , Chang Ho Hyun , Panagiota Papakonstantinou , Yongseok Oh

Linear-scaling electronic structure methods based on the calculation of moments of the underlying electronic Hamiltonian offer a computationally efficient and numerically robust scheme to drive large-scale atomistic simulations, in which…

Materials Science · Physics 2017-01-09 Eunan J. McEniry , Ralf Drautz

The tensor optimized Fermi sphere (TOFS) method is applied first for the study of the property of nuclear matter using the Argonne V4' $NN$ potential. In the TOFS method, the correlated nuclear matter wave function is taken to be a…

Nuclear Theory · Physics 2018-08-27 Taiichi Yamada , Takayuki Myo , Hisashi Horiuchi , Kiyomi Ikeda , Hiroshi Toki

The knowledge of the nuclear level density is necessary for understanding various reactions including those in the stellar environment. Usually the combinatorics of Fermi-gas plus pairing is used for finding the level density. Recently a…

Nuclear Theory · Physics 2016-06-22 Roman Sen'kov , Vladimir Zelevinsky

Fermi operator expansion (FOE) methods are powerful alternatives to diagonalization type methods for solving Kohn-Sham density functional theory (KSDFT). One example is the pole expansion and selected inversion (PEXSI) method, which…

Computational Physics · Physics 2017-10-25 Weile Jia , Lin Lin

In the domain of Fermi energy, it is extremely complex to isolate experimentally fragments and particles issued from the cooling of a hot nucleus produced during a heavy ion collision. This paper presents a new method to characterize more…

Kohn-Sham density functional theory calculations using conventional diagonalization based methods become increasingly expensive as temperature increases due to the need to compute increasing numbers of partially occupied states. We present…

Chemical Physics · Physics 2022-03-23 Qimen Xu , Xin Jing , Boqin Zhang , John E. Pask , Phanish Suryanarayana

A correction to the nuclear functional is proposed in order to improve the density of states around the Fermi surface. The induced effect of this correction is to produce a surface-peaked effective mass, whose mean value can be tuned to get…

We present a method to compute the Fermi function of the Hamiltonian for a system of independent fermions, based on an exact decomposition of the grand-canonical potential. This scheme does not rely on the localization of the orbitals and…

Materials Science · Physics 2009-11-13 Michele Ceriotti , Thomas Kuehne , Michele Parrinello

Nuclear caloric curves have been analyzed using an expanding Fermi gas hypothesis to extract average nuclear densities. In this approach the observed flattening of the caloric curves reflects progressively increasing expansion with…

Nuclear Experiment · Physics 2009-11-07 J. B. Natowitz , K. Hagel , Y. Ma , M. Murray , L. Qin , S. Shlomo , R. Wada , J. Wang

An implicit purification scheme is proposed for calculation of the temperature-dependent, grand canonical single-particle density matrix, given as a Fermi operator expansion in terms of the Hamiltonian. The computational complexity is shown…

Materials Science · Physics 2009-11-10 Anders M. N. Niklasson

We present an accurate and efficient real-space formulation of the Hellmann-Feynman stress tensor for $\mathcal{O}(N)$ Kohn-Sham density functional theory (DFT). While applicable at any temperature, the formulation is most efficient at high…

Computational Physics · Physics 2020-08-26 Abhiraj Sharma , Sebastien Hamel , Mandy Bethkenhagen , John E. Pask , Phanish Suryanarayana

We investigate Fermi gases at finite temperature for which the in-medium effective mass may not be constant as a function of the density, the temperature, or the chemical potential. We suggest a formalism that separates the terms for which…

Nuclear Theory · Physics 2023-07-17 Mariana Dutra , Odilon Lourenço , Jérôme Margueron
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