370 research outputs found
Distortion and electric field control of band structure of silicene
Density functional theory with local density approximation for exchange and
correlation functional is used to tune the electronic band structure of
silicene monolayer. The cohesive energy of free standing monolayer is
increasing (decreasing) with external electric field (distortion). Electrons in
silicene behave like Dirac fermions, when the bond angle between the Si atoms
is larger than . Large distortions destroy the electronic
structure of silicene and silicene is no longer a semi-metallic material, and
the distorted silicene acts like an -doped system. Electric field opens a
band gap around point in the Brillouin zone, which increases with electric
field. The bond angle between the Si atoms is a key player to determine the
presence or absence of Dirac cones in silicene.Comment: Europhysics Lett. Accepted (2014
Strain-induced half-metallic ferromagnetism in zinc blende CrP/MnP superlattice: First-principles study
Using first-principles calculations within generalized gradient
approximation, the electronic and magnetic properties of zinc blende (zb)
CrP/MnP superlattice are investigated. The equilibrium lattice constant is
calculated to be \AA. The stability of ferromagnetic zb CrP/MnP
superlattice against antiferromagnetism is considered and it is found that the
ferromagnetic CrP/MnP superlattice is more stable than the antiferromagnetic
one. It is shown that at the equilibrium lattice constant the CrP/MnP
superlattice does not show any half metallicity mainly due to the minority
states of Cr and Mn. However, if strain is imposed on the CrP/MnP
superlattice then the minority electrons shift to higher energies and
the proposed superlattice becomes a half-metal ferromagnet. The effect of
tetragonal and orthorhombic distortions on the half metallicity of zb CrP/MnP
superlattice is also discussed. It is also shown that InP-CrP/MnP/InP is a true
half-metal ferromagnet. The half metallicity and magnetization of these
superlattices are robust against tetragonal/ orthorhombic deformation.Comment: 5 pages, 4 figure
Magnetic monolayer LiN: Density Functional Theory Calculations
Density functional theory (DFT) calculations are used to investigate the
electronic and magnetic structures of a two-dimensional (2D) monolayer
LiN. It is shown that bulk LiN is a non-magnetic semiconductor. The
non-spinpolarized DFT calculations show that electrons of N in 2D LiN
form a narrow band at the Fermi energy due to a low coordination
number, and the density of states at the Fermi energy ()) is
increased as compared with bulk LiN. The large ) shows
instability towards magnetism in Stoner's mean field model. The spin-polarized
calculations reveal that 2D LiN is magnetic without intrinsic or impurity
defects. The magnetic moment of 1.0\, in 2D LiN is mainly
contributed by the electrons of N, and the band structure shows
half-metallic behavior. {Dynamic instability in planar LiN monolayer is
observed, but a buckled LiN monolayer is found to be dynamically stable.}
The ferromagnetic (FM) and antiferromagnetic (AFM) coupling between the N atoms
is also investigated to access the exchange field strength. {We found that
planar (buckled) 2D LiN is a ferromagnetic material with Curie
temperature of 161 (572) K.}Comment: Euro Phys. Lett. 2017 (Accepted
Adjunct Instructors’ Opportunities for Learning Through Engagement with a Research-Based Mathematics Curriculum
There is a growing need to retain students in STEM fields and majors in the U.S. Improving students’ experience in early mathematics courses like Precalculus can influence students’ decisions to remain in STEM fields. Teachers can play an important role in providing effective learning experiences to the students. Supporting teachers and providing professional development can help the teachers in facilitating student learning. When it comes to implementing research-based mathematics curricula, teachers are key players in making the curriculum come alive inside their classrooms. The challenges that teachers face when implementing a research-based mathematics curriculum can provide opportunities for their own learning. As they engage with the curricular resources, the new curriculum challenges the teachers’ current knowledge and teaching practice. In this dissertation I have explored three adjunct instructors’ engagement with a research-based mathematics curriculum over the course of two semesters. Engagement with the curricular resources provided opportunities for their learning, as the instructors planned and enacted the curriculum, discussed it while collaborating with colleagues or reflecting. Some of these opportunities were availed and some were left unexplored. Findings of this study have implications for developing effective professional development programs for adjunct instructors
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