1,188 research outputs found
A generalized exchange-correlation functional: the Neural-Networks approach
A Neural-Networks-based approach is proposed to construct a new type of
exchange-correlation functional for density functional theory. It is applied to
improve B3LYP functional by taking into account of high-order contributions to
the exchange-correlation functional. The improved B3LYP functional is based on
a neural network whose structure and synaptic weights are determined from 116
known experimental atomization energies, ionization potentials, proton
affinities or total atomic energies which were used by Becke in his pioneer
work on the hybrid functionals [J. Chem. Phys. , 5648 (1993)]. It
leads to better agreement between the first-principles calculation results and
these 116 experimental data. The new B3LYP functional is further tested by
applying it to calculate the ionization potentials of 24 molecules of the G2
test set. The 6-311+G(3{\it df},2{\it p}) basis set is employed in the
calculation, and the resulting root-mean-square error is reduced to 2.2
kcalmol in comparison to 3.6 kcalmol of
conventional B3LYP/6-311+G(3{\it df},2{\it p}) calculation.Comment: 10 pages, 1figur
Dissipative time-dependent quantum transport theory: quantum interference and phonon induced decoherence dynamics
A time-dependent inelastic electron transport theory for strong
electron-phonon interaction is established via the equations of motion method
combined with the small polaron transformation. In this work, the dissipation
via electron-phonon coupling is taken into account in the strong coupling
regime, which validates the small polaron transformation. The corresponding
equations of motion are developed, which are used to study the quantum
interference effect and phonon-induced decoherence dynamics in molecular
junctions. Numerical studies show clearly quantum interference effect of the
transport electrons through two quasi-degenerate states with different coupling
to the leads. We also found that the quantum interference can be suppressed by
the electron-phonon interaction where the phase coherence is destroyed by
phonon scattering. This indicates the importance of electron-phonon interaction
in systems with prominent quantum interference effect
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