46 research outputs found
Relationship between long-range charge-transfer excitation energy error and integer discontinuity in Kohn-Sham theory
Charge-transfer (CT) electronic excitation energies are known to be very poorly predicted by time-dependent density functional theory (TDDFT) using local exchange-correlation functionals. Insight into this observation is provided by a simple analysis of intermolecular CT excitations at infinite separation. It is argued that the first TDDFT CT excitation energy approximately underestimates the experimental excitation by the average of the integer discontinuities of the donor and acceptor molecules; errors are of the order of several electron volts
Nicholas Charles Handy. 17 June 1941 - 2 October 2012
Nicholas Handy made significant contributions in the applications of quantum mechanics to molecules. In an academic career at Cambridge University he was involved with many advances in the computational methods that have turned quantum chemistry into a central tool for understanding modern molecular science
Exchange-correlation energy densities for two-dimensional systems from quantum dot ground-states
In this paper we present a new approach how to extract polarization-dependent
exchange-correlation energy densities for two-dimensional systems from
reference densities and energies of quantum dots provided by exact
diagonalization. Compared with results from literature we find systematic
corrections for all polarizations in the regime of high densities.Comment: 7 figures. submitted to Phys. Rev.
Comparative evaluation of a new lactation curve model for pasture-based Holstein-Friesian dairy cows
A function-based typology for Earth’s ecosystems
As the United Nations develops a post-2020 global biodiversity framework for the Convention on Biological Diversity, attention is focusing on how new goals and targets for ecosystem conservation might serve its vision of ‘living in harmony with nature’1,2. Advancing dual imperatives to conserve biodiversity and sustain ecosystem services requires reliable and resilient generalizations and predictions about ecosystem responses to environmental change and management3. Ecosystems vary in their biota4, service provision5 and relative exposure to risks6, yet there is no globally consistent classification of ecosystems that reflects functional responses to change and management. This hampers progress on developing conservation targets and sustainability goals. Here we present the International Union for Conservation of Nature (IUCN) Global Ecosystem Typology, a conceptually robust, scalable, spatially explicit approach for generalizations and predictions about functions, biota, risks and management remedies across the entire biosphere. The outcome of a major cross-disciplinary collaboration, this novel framework places all of Earth’s ecosystems into a unifying theoretical context to guide the transformation of ecosystem policy and management from global to local scales. This new information infrastructure will support knowledge transfer for ecosystem-specific management and restoration, globally standardized ecosystem risk assessments, natural capital accounting and progress on the post-2020 global biodiversity framework
Association of common genetic variants with brain microbleeds
OBJECTIVE: To identify common genetic variants associated with the presence of brain microbleeds (BMBs). METHODS: We performed geno
Analytic derivatives of potential energy surface
SIGLEAvailable from British Library Document Supply Centre-DSC:D064102 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Density Scaling of Noninteracting Kinetic Energy Functionals
The influence of imposing an approximate density scaling condition on a noninteracting kinetic energy functional is investigated. A simple generalized gradient approximation (GGA) is presented, which satisfies both the density scaling condition and the usual coordinate scaling condition; the remaining multiplicative constant is determined from an energy criterion. In post-Kohn–Sham calculations, noninteracting kinetic energies of the closed-shell molecules of the G1 set determined using the GGA are a modest improvement over those determined using the corresponding local functional, which does not satisfy the density scaling condition. Potential energy curves of CO, F2, and P2 exhibit binding with the GGA, compared to purely repulsive curves with the local functional. Adjusting the exponent in the GGA form in order to optimize energy accuracy violates the density scaling condition, and two of the diatomics no longer exhibit binding. Results are compared with those from other local/GGA functionals in the literature