24 research outputs found
Ab-initio quantum transport simulation of self-heating in single-layer 2-D materials
Through advanced quantum mechanical simulations combining electron and phonon
transport from first-principles self-heating effects are investigated in n-type
transistors with a single-layer MoS2, WS2, and black phosphorus as channel
materials. The selected 2-D crystals all exhibit different phonon-limited
mobility values, as well as electron and phonon properties, which has a direct
influence on the increase of their lattice temperature and on the power
dissipated inside their channel as a function of the applied gate voltage and
electrical current magnitude. This computational study reveals (i) that
self-heating plays a much more important role in 2-D materials than in Si
nanowires, (ii) that it could severely limit the performance of 2-D devices at
high current densities, and (iii) that black phosphorus appears less sensitive
to this phenomenon than transition metal dichalcogenides
Electronic Properties of Lithiated SnO-based Anode Materials
In this paper we use an ab-initio quantum transport approach to study the
electron current flowing through lithiated SnO anodes for potential
applications in Li-ion batteries. By investigating a set of lithiated
structures with varying lithium concentrations, it is revealed that LixSnO can
be a good conductor, with values comparable to bulk -Sn and Li. A deeper
insight into the current distribution indicates that electrons preferably
follow specific trajectories, which offer superior conducting properties than
others. These channels have been identified and it is shown here how they can
enhance or deteriorate the current flow in lithiated anode materials
Lithiation-delithiation cycles of amorphous Si nanowires investigated by molecular dynamics simulations
The atomistic mechanisms during lithiation and delithiation of amorphous Si
nanowires (-SiNW) have been investigated over cycles by molecular dynamics
simulations. First, the Modified Embedded Atom Method (MEAM) potential from Cui
et al. [J. Power Sources. 2012, (207) 150] has been further optimized on static
(LiSi alloy phases and point defect energies) and on dynamic properties (Li
diffusion) to reproduce the lithiation of small crystalline Si nanowires
calculated at the {\it ab initio} level. The lithiation of -SiNW reveals a
two-phase process of lithiation with a larger diffusion interface compared to
crystalline Si lithiation. Compressive axial stresses are observed in the
amorphous SiLi alloy outer shell. They are easily released thanks to the
soft glassy behavior of the amorphous alloy. Conversely, in crystalline SiNW,
the larger stress in the narrow crystalline lithiated interface is hardly
released and requires a phase transformation to amorphous to operate, which
delays the lithiation. The history of the charge-discharge cycles as well as
the temperature appear as driving forces for phase transformation from
amorphous LiSi alloy to the more stable crystalline phase counterpart. Our
work suggest that a full delithiation could heal the SiNWs to improve the life
cycles of Li-ion batteries with Si anode.Comment: 11 pages, 8 figures
Money Manager Application
An android application meant to serve as a money manage