Article
Physics, Fluids & Plasmas
Diego Escribano, Jose A. Cuesta
Summary: Ensemble models of graphs, especially exponential random graphs (ERGs), are important tools in studying complex networks, particularly in the analysis of social networks. This paper presents a technique borrowed from the statistical mechanics of lattice gases to solve Strauss's model of transitive networks. The method accurately describes even small networks and can be extended to networks with different types of nodes.
Article
Multidisciplinary Sciences
Alexander Ryabov, Iskander Akhatov, Petr Zhilyaev
Summary: Density functional theory is a primary method for solving the many-body Schrodinger equation, and its accuracy relies on the development of exchange-correlation (XC) functional approximations. The neural network approach offers a unified approach to parametrize the XC functional by interpolating data from higher precision theories. Our developed neural network XC functional converges in the self-consistent cycle and provides reasonable energies for different systems.
SCIENTIFIC REPORTS
(2022)
Article
Chemistry, Physical
Ulises A. Vergara-Beltran, Juan I. Rodriguez
Summary: A differential evolution global optimization method for all-electron orbital-free density functional theory is proposed in this study. The method does not require information about function derivatives and can be applied to optimization problems dealing with non-differentiable functionals or functionals with non-closed forms.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Mohammad Goli, Shant Shahbazian
Summary: This paper introduces and computationally implements the two-component density functional theory (TC-DFT), a first principles method that treats electrons and positive muons as quantum particles. It proposes a new electron-positive muon correlation functional to improve computational accuracy. The capability of this method is demonstrated through its application to a benchmark set of muonic organic molecules, setting the stage for the development of accurate electron-positive muon functionals.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
C. M. Horowitz, C. R. Proetto, J. M. Pitarke
Summary: This article investigates the behavior of the main components of the orbital-free density-functional theory on metal slabs, deriving explicit density functionals and conducting numerical calculations. The results show that a generally valid kinetic-energy density functional can be obtained for realistic many-particle fermionic systems.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Aparna Gangwar, Satya S. Bulusu, Arup Banerjee
Summary: In this study, a neural network-based representation for the Pauli potential was developed, allowing for the calculation of Pauli kinetic energy without the need for a functional derivative. This approach can be applied to orbital-free density functional theory-based methods, serving as an important advancement in machine learning-based techniques.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Subrata Jana, Lucian A. Constantin, Prasanjit Samal
Summary: We propose a realistic density functional approximation based on a semilocal indicator that exhibits good screening properties. The local band model shows remarkable density scaling behaviors and is applicable to various atoms. We introduce the LDAg correlation functional, which correctly calculates the correlation energy of atoms and shows improvement in ionization potential.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
C. M. Horowitz, C. R. Proetto, J. M. Pitarke
Summary: In this paper, an alternative approach is proposed to construct the exchange-correlation enhancement factor of density-functional theory based on the ab initio calculation of the exact exchange energy density. The approach is implemented using jellium-slab exact-exchange self-consistent calculations. The results show that the proposed method yields exchange energies that approach the exact exchange energy in the two-dimensional limit.
Article
Chemistry, Physical
Peter Kovacs, Fabien Tran, Peter Blaha, Georg K. H. Madsen
Summary: This study systematically explores the space of generalized gradient approximation (GGA) and meta-GGA (mGGA) exchange approximations by training new functionals, aiming to improve accurate predictions of lattice parameter, cohesive energy, and bandgap. The trained functionals perform similarly to specialized functionals for bandgap predictions and outperform them for the other two properties.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Multidisciplinary Sciences
Qiang Xu, Cheng Ma, Wenhui Mi, Yanchao Wang, Yanming Ma
Summary: The authors present a novel protocol that allows for the application of nonlocal pseudopotentials to orbital-free density functional theory (OF-DFT). They have developed a theoretical scheme that defies the traditional belief and enables the direct use of nonlocal pseudopotentials in OF-DFT.
NATURE COMMUNICATIONS
(2022)
Article
Chemistry, Physical
Daniel Gibney, Jan-Niklas Boyn, David A. Mazziotti
Summary: Researchers demonstrate how to transform DFT into a one-electron reduced-density-matrix (1-RDM) functional theory to address the limitations of accurately describing the electronic structure of strongly correlated systems. This method retains favorable computational scaling compared to traditional DFT and achieves substantial improvements in the description of static correlation in chemical structures and processes.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Astronomy & Astrophysics
Ulrich K. Beckering Vinckers, Alvaro de la Cruz-Dombriz, Ivan Kolar, Francisco J. Maldonado Torralba, Anupam Mazumdar
Summary: In this study, we introduce ghost-free infinite-derivative extensions of spherically reduced gravity and CGHS theory in two-dimensional spacetime. We diagonalize the quadratic action for field perturbations under specific gauge choices and obtain ghost-free infinite-derivative modifications of SRG and CGHS theories. Nonlocal modifications to the linearized Schwarzschild and black-hole solutions are analyzed within these modified theories.
Article
Chemistry, Physical
Ahmad W. Huran, Hai-Chen Wang, Alfonso San-Miguel, Miguel A. L. Marques
Summary: The theoretical study reveals that an atomically thin, two-dimensional layer formed by positioning atoms at the vertices of a classical Pythagorean tiling exhibits an unusual geometrical pattern, stable only for the halogens Cl, Br, and I. This Pythagorean structure shows competitive energy properties and semiconducting behavior, with an unusual band structure composed of mobile holes and heavy electrons. Additionally, the structure is soft with low energy flexural mode and can be identified through breathing-like modes using Raman transitions.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Mathematics, Applied
Kaijie Xue
Summary: We propose a methodology for testing two-sample means in high-dimensional functional data that does not require a decaying pattern on eigenvalues of the functional data. To the best of our knowledge, we are the first to consider and address such a problem. Specifically, we devise a confidence region for the mean curve difference between two samples, which directly establishes a rigorous inferential procedure based on the multiplier bootstrap. In addition, the proposed test permits the functional observations in each sample to have mutually different distributions and arbitrary correlation structures, which is regarded as the desired property of distribution/correlation-free, leading to a more challenging scenario for theoretical development.
SCIENCE CHINA-MATHEMATICS
(2023)
Article
Mathematics, Applied
Bin Gao, Guanghu Hu, Yang Kuang, Xin Liu
Summary: All-electron calculations are crucial in density functional theory, and improving computational efficiency is a challenging task. In this paper, an orthogonalization-free algorithm framework is proposed to solve the nonlinear eigenvalue problem and the total energy minimization problem without invoking orthogonalization in each iteration, thereby enhancing computational efficiency and parallel scalability.
SIAM JOURNAL ON SCIENTIFIC COMPUTING
(2022)
Article
Physics, Condensed Matter
J. Keski-Rahkonen, P. J. J. Luukko, S. Aberg, E. Rasanen
JOURNAL OF PHYSICS-CONDENSED MATTER
(2019)
Article
Physics, Multidisciplinary
Rainer Klages, Sol Selene Gil Gallegos, Janne Solanpaa, Mika Sarvilahti, Esa Rasanen
PHYSICAL REVIEW LETTERS
(2019)
Article
Physics, Multidisciplinary
S. Gil-Gallegos, R. Klages, J. Solanpaa, E. Rasanen
EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS
(2019)
Article
Physics, Multidisciplinary
J. Keski-Rahkonen, A. Ruhanen, E. J. Heller, E. Rasanen
PHYSICAL REVIEW LETTERS
(2019)
Article
Multidisciplinary Sciences
Matti Molkkari, Giorgio Angelotti, Thorsten Emig, Esa Rasanen
SCIENTIFIC REPORTS
(2020)
Article
Physics, Multidisciplinary
K. Bencheikh, A. Putaja, E. Rasanen
Summary: By utilizing the propagator of linear potential, the Airy gas model originally developed for three-dimensional edge electron gas is extended to systems with reduced dimensions. Explicit expressions for edge particle density and corresponding kinetic energy density in all dimensions are derived, which adhere to the local virial theorem. A functional relationship between positive KED and particle density with gradients is established, with the KED functional reducing to that of the Thomas-Fermi model in d dimensions in the limit of local-density approximation.
JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL
(2021)
Article
Computer Science, Interdisciplinary Applications
R. Duda, J. Keski-Rahkonen, J. Solanpaa, E. Rasanen
Summary: TINIE is a state-of-the-art quantum transport simulation framework that can efficiently perform various calculations and has a wide range of applications. It supports calculations ranging from transmission and conductivity to local density of states, and can simulate diverse systems while handling impurities and imperfections.
COMPUTER PHYSICS COMMUNICATIONS
(2022)
Article
Multidisciplinary Sciences
Alvar Daza, Eric J. Heller, Anton M. Graf, Esa Rasanen
Summary: We report unexpected classical and quantum dynamics of a wave propagating in a periodic potential in high Brillouin zones. Branched flow appears at wavelengths shorter than the typical length scale of the ordered periodic structure and for energies above the potential barrier. The strongest branches remain stable indefinitely and may create linear dynamical channels, termed superwires, associated with a superlattice.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2021)
Article
Physics, Multidisciplinary
Esko Toivonen, Matti Molkkari, Esa Rasanen, Lasse Laurson
Summary: Under the symmetry breaking caused by the direction of the driving force, the roughness of elastic interfaces exhibits asymmetry, which can be quantified by computing the spectrum of local scaling exponents.
PHYSICAL REVIEW LETTERS
(2022)
Article
Cardiac & Cardiovascular Systems
Esa Rasanen, Teemu Pukkila, Matias Kanniainen, Minna Miettinen, Rostislav Duda, Jiyeong Kim, Janne Solanpaa, Katriina Aalto-Setala, Ilya Potapov
Summary: The article introduces a new QT correction method, AccuQT, which computes QTc by minimizing the information transfer from R-R to QT intervals. The results show that AccuQT outperforms other commonly used correction methods and has the potential to become the method of choice in clinical studies and drug development.
CARDIOVASCULAR DIGITAL HEALTH JOURNAL
(2023)
Proceedings Paper
Computer Science, Interdisciplinary Applications
Teemu Pukkila, Matti Molkkari, Esa Rasanen
Summary: The study found that while HRV measures show clear differences between driving and being at rest, individuals exhibit highly personalized cardiac responses to the experiment. DDFA analysis provides more detailed information on dynamic HRV changes that are often hidden in conventional measures.
2021 COMPUTING IN CARDIOLOGY (CINC)
(2021)
Article
Materials Science, Multidisciplinary
Alberto Guandalini, Alice Ruini, Esa Rasanen, Carlo A. Rozzi, Stefano Pittalis
Summary: We propose a density functional theory-based approach for calculating fundamental gaps of both finite and periodic 2D electronic systems, with computational cost comparable to standard semilocal forms. By replacing the 2D local density approximation with a more sophisticated yet computationally simple orbital-dependent modeling, promising results are achieved for semiconductor 2D quantum dots and artificial graphene systems, where band structure can be tuned through various methods such as Kekule distortion.
Proceedings Paper
Cardiac & Cardiovascular Systems
Matti Molkkari, Janne Solanpaa, Esa Rasanen
2020 COMPUTING IN CARDIOLOGY
(2020)
Article
Materials Science, Multidisciplinary
Alberto Guandalini, Carlo A. Rozzi, Esa Rasanen, Stefano Pittalis
Article
Multidisciplinary Sciences
Jiyeong Kim, Disheet Shah, Ilya Potapov, Joonas Latukka, Katriina Aalto-Setala, Esa Rasanen
SCIENTIFIC REPORTS
(2019)