Results 341 to 350 of about 13,126,412 (380)

Density-equicontinuity and Density-sensitivity

Acta Mathematica Sinica, English Series, 2021
In this paper we introduce the notions of (Banach) density-equicontinuity and density-sensitivity. On the equicontinuity side, it is shown that a topological dynamical system is density-equicontinuous if and only if it is Banach density-equicontinuous. On the sensitivity side, we introduce the notion of density-sensitive tuple to characterize the multi-
Jie Li, Siming Tu
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Improved methods for building protein models in electron density maps and the location of errors in these models.

Acta Crystallographica Section A Foundations of Crystallography, 1991
Map interpretation remains a critical step in solving the structure of a macromolecule. Errors introduced at this early stage may persist throughout crystallographic refinement and result in an incorrect structure.
T. Jones, J. Zou, S. Cowan, M. Kjeldgaard, Serge HAGgGE   +4 more
semanticscholar   +1 more source

Toward reliable density functional methods without adjustable parameters: The PBE0 model

, 1999
We present an analysis of the performances of a parameter free density functional model (PBE0) obtained combining the so called PBE generalized gradient functional with a predefined amount of exact exchange.
C. Adamo, V. Barone
semanticscholar   +1 more source

Correction of Density Estimators that are not Densities

Scandinavian Journal of Statistics, 2003
Abstract. Several old and new density estimators may have good theoretical performance, but are hampered by not being bona fide densities; they may be negative in certain regions or may not integrate to 1. One can therefore not simulate from them, for example.
Ingrid K. Glad, N. G. Ushakov, Nils Lid Hjort   +2 more
openaire   +2 more sources

Ab Initio Calculation of Vibrational Absorption and Circular Dichroism Spectra Using Density Functional Force Fields

, 1994
: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio.
P. Stephens, F. Devlin, C. Chabalowski, M. Frisch   +3 more
semanticscholar   +1 more source

A New Mixing of Hartree-Fock and Local Density-Functional Theories

, 1993
Previous attempts to combine Hartree–Fock theory with local density‐functional theory have been unsuccessful in applications to molecular bonding. We derive a new coupling of these two theories that maintains their simplicity and computational efficiency,
A. Becke
semanticscholar   +1 more source

Density-functional approximation for the correlation energy of the inhomogeneous electron gas.

Physical Review B (Condensed Matter), 1986
Langreth and Mehl (LM) and co-workers have developed a useful spin-density functional for the correlation energy of an electronic system. Here the LM functional is improved in two ways: (1) The natural separation between exchange and correlation is made,
J. Perdew
semanticscholar   +1 more source

Multivariate Density Estimation, Theory, Practice and Visualization

, 1992
Representation and Geometry of Multivariate Data. Nonparametric Estimation Criteria. Histograms: Theory and Practice. Frequency Polygons. Averaged Shifted Histograms. Kernel Density Estimators.
D. W. Scott
semanticscholar   +1 more source

Density matrices from densities

Chemical Physics Letters, 1990
Abstract The density matrix can be reconstructed from the density alone, if a basis set is used whose product functions are all linearly independent. This is not the case for quantum-chemical basis sets, except for small s-type sets. In case of the idempotency constraint on the density matrix - justified in the density functional approach, but in ...
W. H. E. Schwarz, B. Müller
openaire   +2 more sources

Design of capacity-approaching irregular low-density parity-check codes

IEEE Transactions on Information Theory, 2001
We design low-density parity-check (LDPC) codes that perform at rates extremely close to the Shannon capacity. The codes are built from highly irregular bipartite graphs with carefully chosen degree patterns on both sides. Our theoretical analysis of the
T. Richardson, A. Shokrollahi, R. Urbanke   +2 more
semanticscholar   +1 more source