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We present a new second order complete active space self-consistent field implementation to converge wavefunctions for both large active spaces and large atomic orbital (AO) bases. Our algorithm decouples the active space wavefunction…

Chemical Physics · Physics 2017-08-23 Qiming Sun , Jun Yang , Garnet Kin-Lic Chan

Machine learning is employed to build an energy density functional for self-bound nuclear systems for the first time. By learning the kinetic energy as a functional of the nucleon density alone, a robust and accurate orbital-free density…

Nuclear Theory · Physics 2022-03-21 X. H. Wu , Z. X. Ren , P. W. Zhao

Recently, sparsity-based algorithms are proposed for super-resolution spectrum estimation. However, to achieve adequately high resolution in real-world signal analysis, the dictionary atoms have to be close to each other in frequency,…

Machine Learning · Statistics 2015-06-05 Yiyuan She , Huanghuang Li , Jiangping Wang , Dapeng Wu

We formulate and implement Cyclic Density Functional Theory (Cyclic DFT) -- a self-consistent first principles simulation method for nanostructures with cyclic symmetries. Using arguments based on Group Representation Theory, we rigorously…

Materials Science · Physics 2017-03-16 Amartya S. Banerjee , Phanish Suryanarayana

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 present enhancements to the computational efficiency of exact exchange calculations using the density matrix and local support functions. We introduce a numerical method which avoids the explicit calculation the four-center two-electron…

Chemical Physics · Physics 2016-11-25 Lionel A. Truflandier , Tsuyoshi Miyazaki , David R. Bowler

We present a real-space formulation for isotropic Fourier-space preconditioners used to accelerate the self-consistent field iteration in Density Functional Theory calculations. Specifically, after approximating the preconditioner in…

Computational Physics · Physics 2020-01-08 Shashikant Kumar , Qimen Xu , Phanish Suryanarayana

Novel results for the self-consistent single-particle spectral function and self-energy are presented for non-degenerate one-component Coulomb systems at various densities and temperatures. The GW^0-method for the dynamical self-energy is…

Plasma Physics · Physics 2009-11-13 Carsten Fortmann

Possible short and semi-short positive energy, unitary representations of the Osp(2N|4) superconformal group in three dimensions are discussed. Corresponding character formulae are obtained, consistent with character formulae for the…

High Energy Physics - Theory · Physics 2014-11-18 F. A. Dolan

Density functional theory (DFT) has emerged as one of the most versatile and lucrative approaches in electronic structure calculations of many-electron systems in past four decades. Here we give an account of the development of a…

Chemical Physics · Physics 2019-04-19 Abhisek Ghosal , Amlan K. Roy

We study equivariant families of discrete Hamiltonians on amenable geometries and their integrated density of states (IDS). We prove that the eigenspace of a fixed energy is spanned by eigenfunctions with compact support. The size of a jump…

Metric Geometry · Mathematics 2018-09-28 Daniel Lenz , Ivan Veselic'

Linear scaling methods provide total energy, but no energy levels and canonical wavefuctions. From the density matrix computed through the density matrix purification methods, we propose an order-N (O(N)) method for calculating both the…

Materials Science · Physics 2007-06-27 H. J. Xiang , Jinlong Yang , J. G. Hou , Qingshi Zhu

We describe a method of solving the nuclear Skyrme-Hartree-Fock problem by using a deformed Cartesian harmonic oscillator basis. The complete list of expressions required to calculate local densities, total energy, and self-consistent…

Nuclear Theory · Physics 2009-10-30 J. Dobaczewski , J. Dudek

We present a generalization of the Li, Nunes and Vanderbilt density-matrix method to the case of a non-orthogonal set of basis functions. A representation of the real-space density matrix is chosen in such a way that only the overlap…

Condensed Matter · Physics 2009-10-22 R. W. Nunes , David Vanderbilt

A brief review of the SIESTA project is presented in the context of linear-scaling density-functional methods for electronic-structure calculations and molecular-dynamics simulations of systems with a large number of atoms. Applications of…

Materials Science · Physics 2015-06-25 Emilio Artacho , Daniel Sanchez-Portal , Pablo Ordejon , Alberto Garcia , Jose M. Soler

Exploratory variational pseudopotential density functional calculations are performed for the electronic properties of many-electron systems in the 3D cartesian coordinate grid (CCG). The atom-centered localized gaussian basis set,…

Chemical Physics · Physics 2015-05-18 Amlan K Roy

The isoelectronic series of Be, Ne and Si are investigated using a variational determination of the second-order density matrix. A semidefinite program was developed that exploits all rotational and spin symmetries in the atomic system. We…

Strongly Correlated Electrons · Physics 2009-09-14 Brecht Verstichel , Helen van Aggelen , Dimitri Van Neck , Paul W. Ayers , Patrick Bultinck

Large-scale density functional theory (DFT) calculations provide a powerful tool to investigate the atomic and electronic structure of materials with complex structures. This article reviews a large-scale DFT calculation method, the…

Materials Science · Physics 2022-08-31 Ayako Nakata , David R. Bowler , Tsuyoshi Miyazaki

We present a systematic study of the performance of numerical pseudo-atomic orbital basis sets in the calculation of dielectric matrices of extended systems using the self-consistent Sternheimer approach of [F. Giustino et al., Phys. Rev. B…

Materials Science · Physics 2015-06-04 Hannes Hübener , Miguel A. Pérez-Osorio , Pablo Ordejón , Feliciano Giustino

This article improves on existing methods to estimate the spectral density of stationary and nonstationary time series assuming a Gaussian process prior. By optimising an appropriate eigendecomposition using a smoothing spline covariance…

Methodology · Statistics 2022-06-01 Nick James , Max Menzies