162 research outputs found
Polaronic distortion and vacancy-induced magnetism in MgO
The electronic structure of the neutral and singly charged Mg vacancy in MgO
is investigated using density functional theory. For both defects, semilocal
exchange correlation functionals such as the local spin density approximation
incorrectly predict a delocalized degenerate ground state. In contrast
functionals that take strong correlation effects into account predict a
localized solution, in agreement with spin resonance experiments. Our results,
obtained with the HSE hybrid, atomic self-interaction corrected and LDA+U
functionals, provide a number of constraints to the possibility of
ferromagnetism in hole doped MgO
The Levy-Lieb embedding of density functional theory and its Quantum Kernel: Illustration for the Hubbard Dimer using near-term quantum algorithms
The constrained-search formulation of Levy and Lieb provides a concrete
mapping from N-representable densities to the space of N-particle wavefunctions
and explicitly defines the universal functional of density functional theory.
We numerically implement the Levy-Lieb procedure for a paradigmatic lattice
system, the Hubbard dimer, using a modified variational quantum eigensolver
approach. We demonstrate density variational minimization using the resulting
hybrid quantum-classical scheme featuring real-time computation of the
Levy-Lieb functional along the search trajectory. We further illustrate a
fidelity based quantum kernel associated with the density to pure-state
embedding implied by the Levy-Lieb procedure and employ the kernel for learning
observable functionals of the density. We study the kernel's ability to
generalize with high accuracy through numerical experiments on the Hubbard
dimer.Comment: 9 pages, 6 figure
Ab initio study of electron transport in dry poly(G)-poly(C) A-DNA strands
The bias-dependent transport properties of short poly(G)-poly(C) A-DNA
strands attached to Au electrodes are investigated with first principles
electronic transport methods. By using the non- equilibrium Green's function
approach combined with self-interaction corrected density functional theory, we
calculate the fully self-consistent coherent I-V curve of various double-strand
polymeric DNA fragments. We show that electronic wave-function localization,
induced either by the native electrical dipole and/or by the electrostatic
disorder originating from the first few water solvation layers, drastically
suppresses the magnitude of the elastic conductance of A-DNA oligonucleotides.
We then argue that electron transport through DNA is the result of
sequence-specific short-range tunneling across a few bases combined with
general diffusive/inelastic processes.Comment: 15 pages, 13 figures, 1 tabl
First-principles study of high conductance DNA sequencing with carbon nanotube electrodes
Rapid and cost-effective DNA sequencing at the single nucleotide level might
be achieved by measuring a transverse electronic current as single-stranded DNA
is pulled through a nano-sized pore. In order to enhance the electronic
coupling between the nucleotides and the electrodes and hence the current
signals, we employ a pair of single-walled close-ended (6,6) carbon nanotubes
(CNTs) as electrodes. We then investigate the electron transport properties of
nucleotides sandwiched between such electrodes by using first-principles
quantum transport theory. In particular we consider the extreme case where the
separation between the electrodes is the smallest possible that still allows
the DNA translocation. The benzene-like ring at the end cap of the CNT can
strongly couple with the nucleobases and therefore both reduce conformational
fluctuations and significantly improve the conductance. The optimal molecular
configurations, at which the nucleotides strongly couple to the CNTs, and which
yield the largest transmission, are first identified. Then the electronic
structures and the electron transport of these optimal configurations are
analyzed. The typical tunneling currents are of the order of 50 nA for voltages
up to 1 V. At higher bias, where resonant transport through the molecular
states is possible, the current is of the order of several A. Below 1 V
the currents associated to the different nucleotides are consistently
distinguishable, with adenine having the largest current, guanine the
second-largest, cytosine the third and finally thymine the smallest. We further
calculate the transmission coefficient profiles as the nucleotides are dragged
along the DNA translocation path and investigate the effects of configurational
variations. Based on these results we propose a DNA sequencing protocol
combining three possible data analysis strategies.Comment: 12 pages, 17 figures, 3 table
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