Crystallization of dipolar hard spheres: Density functional results

1998 ◽  
Vol 109 (3) ◽  
pp. 1062-1069 ◽  
Author(s):  
Sabine Klapp ◽  
Frank Forstmann
Keyword(s):  
Density Functional ◽  
Hard Spheres ◽  
Functional Results

Density Functional Theory for Small Systems: Hard Spheres in a Closed Spherical Cavity

1997 ◽  
Vol 79 (13) ◽  
pp. 2466-2469 ◽  
Author(s):  
A. González ◽  
J. A. White ◽  
F. L. Román ◽  
S. Velasco ◽  
R. Evans
Keyword(s):  
Density Functional Theory ◽  
Spherical Cavity ◽  
Density Functional ◽  
Hard Spheres ◽  
Functional Theory ◽  
Small Systems

scholarly journals Machine learning the Hubbard U parameter in DFT+U using Bayesian optimization

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Maituo Yu ◽  
Shuyang Yang ◽  
Chunzhi Wu ◽  
Noa Marom
Keyword(s):  
Machine Learning ◽  
Transition Metal Oxides ◽  
Density Functional ◽  
Functional Results ◽  
Bayesian Optimization ◽  
Hybrid Functional ◽  
Band Structures ◽  
Local Exchange ◽  
Functional Theory ◽  
Exchange Correlation

AbstractWithin density functional theory (DFT), adding a Hubbard U correction can mitigate some of the deficiencies of local and semi-local exchange-correlation functionals, while maintaining computational efficiency. However, the accuracy of DFT+U largely depends on the chosen Hubbard U values. We propose an approach to determining the optimal U parameters for a given material by machine learning. The Bayesian optimization (BO) algorithm is used with an objective function formulated to reproduce the band structures produced by more accurate hybrid functionals. This approach is demonstrated for transition metal oxides, europium chalcogenides, and narrow-gap semiconductors. The band structures obtained using the BO U values are in agreement with hybrid functional results. Additionally, comparison to the linear response (LR) approach to determining U demonstrates that the BO method is superior.

Electronic Structure, Magnetism and Spin-Fluctuations in Fe-As Based Superconductors

2008 ◽  
Vol 1148 ◽  
Author(s):  
David Joseph Singh ◽  
Mao-Hua Du ◽  
Lijun Zhang ◽  
Alaska Subedi ◽  
Jiming An
Keyword(s):  
Electronic Structure ◽  
Fermi Surface ◽  
Density Functional ◽  
Density Wave ◽  
Spin Density Wave ◽  
Functional Results ◽  
Spin Fluctuations ◽  
Square Lattice ◽  
Itinerant Magnetism ◽  
Strong Spin

AbstractThe physical properties of the layered iron superconductors and related phases are discussed starting from first principles calculations. The electronic structure is described as that of metallic Fe2+ square lattice sheets with substantial direct Fe-Fe hopping and interactions with the neighboring anionic pnictogens or chalcogens. The materials have a semi-metallic band structure, and in particular the Fermi surface consists of small cylindrical electron sections centered at the zone corner, and compensating hole sections at the zone boundary. The density of states N(EF) is high placing the materials near itinerant magnetism in general, and furthermore the small Fermi surface sections are well nested leading to a tendency towards a spin density wave. Comparison of experimental and density functional results imply the presence of exceptionally strong spin fluctuations in these materials. Superconductivity is discussed within this context.

High-order correlation effects on dynamic hyperpolarizabilities and their geometric derivatives: A comparison with density functional results

2006 ◽  
Vol 124 (11) ◽  
pp. 114101 ◽  
Author(s):  
Magdalena Pecul ◽  
Filip Pawłowski ◽  
Poul Jørgensen ◽  
Andreas Köhn ◽  
Christof Hättig
Keyword(s):  
Density Functional ◽  
Functional Results ◽  
High Order ◽  
Correlation Effects ◽  
High Order Correlation
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