Exploring non-adiabatic approximations to the exchange-correlation functional of TDDFT

A decomposition of the exact exchange-correlation potential of time-dependent density functional theory into an interaction component and a kinetic component offers a new starting point for non-adiabatic approximations. The components are expressed in terms of the exchange-correlation hole and the difference between the one-body density matrix of the interacting and Kohn-Sham systems, which must be approximated in terms of quantities accessible from the Kohn-Sham evolution. We explore several preliminary approximations, evaluate their fulfillment of known exact conditions, and test their performance on simple model systems for which available exact solutions indicate the significance of going beyond the adiabatic approximation.Fil: Fuks, Johanna Ildemar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Lacombe, Lionel. University of New York; Estados UnidosFil: Nielsen, Søren E. B.. Max Planck Institute for the Structure and Dynamics of Matter; Alemania. Center for Free-Electron Laser Science; AlemaniaFil: Maitra, Neepa T.. University of New York; Estados Unido

The Exact Exchange-Correlation Potential in Time-Dependent Density Functional Theory: Choreographing Electrons with Steps and Peaks

The time-dependent exchange-correlation potential has an unusual task in directing fictitious non-interacting electrons to move with exactly the same probability density as true interacting electrons. This has intriguing implications for its structure, especially in the non-perturbative regime, leading to step and peak features that cannot be captured by bootstrapping any ground-state functional approximations. We review what has been learned about these features in the exact exchange-correlation potential in time-dependent density functional theory in the past decade or so, and implications for the performance of simulations when electrons are driven far from any ground-state

Skyrmions and the Nuclear Force

The derivation of the nucleon-nucleon force from the Skyrme model is reexamined. Starting from previous results for the potential energy of quasistatic solutions, we show that a calculation using the Born-Oppenheimer approximation properly taking into account the mixing of nucleon resonances, leads to substantial central attraction. We obtain a potential that is in qualitative agreement with phenomenological potentials. We also study the non-adiabatic corrections, such as the velocity dependent transition potentials, and discuss their importance.Comment: 24 pages, UPR-0124M

Grapevine European catalogue: towards a comprehensive list

Starting from the 1950’s, different European countries have established official lists of grapevine varieties authorized to be cultivated. The objectives of such lists were to limit ambiguous denomination of varieties and the related trade conflicts, as well as the implementation of viticulture recovery politics through the support of certain varieties and the limitation of others. In the same direction, in 1968 the European Union (EU) decided to create a “common catalogue of varieties”, defined as the sum of current national catalogues (Council Directive of 9 April 1968 “on the marketing of material for the vegetative propagation of the vine”, 68/193/EEC, modified). These catalogues (also called “registers”) include all the wine varieties “classified” by each Member State within the framework of the Common Organisation of the Market in wine (Council Directive No 479/2008), as well as all the non-classified varieties (table grape, rootstocks, etc.). For this work, we took the opportunity of the European research program “GrapeGen06”, focused on the study and the preservation of grapevine genetic resources, to contribute to the establishment and improvement of such an European catalogue. The comprehensive survey aims at two objectives: to support the implementation of European regulations on propagation of grapevine plants within the EU, and to assess priority actions, by technical and research institutes, for the conservation of grapevine genetic resources.Peer reviewe

Electron Scattering in Time-Dependent Density Functional Theory

It was recently shown [Y. Suzuki, L. Lacombe, K. Watanabe, and N. T. Maitra, Phys. Rev. Lett. 119, 263401 (2017)] that peak and valley structures in the exact exchange-correlation potential of time-dependent density functional theory are crucial for accurately capturing time-resolved dynamics of electron scattering in a model one-dimensional system. Approximate functionals used today miss these structures and con- sequently underestimate the scattering probability. The dynamics can vary significantly depending on the choice of the initial Kohn-Sham state, and, with a judicious choice, a recently-proposed non-adiabatic ap- proximation provides extremely accurate dynamics on approach to the target but this ultimately also fails to capture reflection accurately. Here we provide more details, using a model of electron-He + as illustration, in both the inelastic and elastic regimes. In the elastic case, the time-resolved picture is contrasted with the time-independent picture of scattering, where the linear response theory of TDDFT can be used to extract transmission and reflection coefficients. Although the exact functional yields identical scattering probabil- ities when used in this way as it does in the time-resolved picture, we show that the currently-available approximate functionals do not, even when they have the correct asymptotic behavior.Comment: 9 pages, 6 figure

Exact time-dependent density-functional theory for nonperturbative dynamics of the helium atom

By inverting the time-dependent Kohn-Sham equation for a numerically exact dynamics of the helium atom, we show that the dynamical step and peak features of the exact correlation potential found previously in one-dimensional models persist for real three-dimensional systems. We demonstrate that the Kohn-Sham and true current densities differ by a rotational component. The results have direct implications for approximate time-dependent density functional theory calculations of atoms and molecules in strong fields, emphasizing the need to go beyond the adiabatic approximation, and highlighting caution in the quantitative use of the Kohn-Sham currentFinancial support from the National Science Foundation Award No. CHE-1940333 (DD) and from the Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under Award No. DESC0020044 (NTM, LL) are gratefully acknowledged. J.F. acknowledges financial support from the European Research Council through Grant No. ERC-2016- StG-714870, and by the Spanish Ministry for Science, Innovation, and Universities: Agencia Estatal de Investigación through Grant No. RTI2018-099737-B-I0