43 research outputs found
First-Principles Phonon Quasiparticle Theory Applied to a Strongly Anharmonic Halide Perovskite
Understanding and predicting lattice dynamics in strongly anharmonic crystals
is one of the long-standing challenges in condensed matter physics. Here we
propose a first-principles method that gives accurate quasiparticle (QP) peaks
of the phonon spectrum with strong anharmonic broadening. On top of the
conventional first-order self-consistent phonon (SC1) dynamical matrix, the
proposed method incorporates frequency renormalization effects by the bubble
self-energy within the QP approximation. We apply the developed methodology to
the strongly anharmonic -CsPbBr that displays phonon instability
within the harmonic approximation in the whole Brillouin zone. While the SC1
theory significantly underestimates the cubic-to-tetragonal phase transition
temperature (\tc) by more than 50\%, we show that our approach yields \tc =
404--423~K, in excellent agreement with the experimental value of 403~K. We
also demonstrate that an accurate determination of QP peaks is paramount for
quantitative prediction and elucidation of lattice thermal conductivity.Comment: 6 pages, 3 figure
First-principles prediction of phase transition of YCo from self-consistent phonon calculations
Recent theoretical study has shown that the hexagonal YCo is dynamically
unstable and distorts into a stable orthorhombic structure. In this study, we
show theoretically that the orthorhombic phase is energetically more stable
than the hexagonal phase in the low-temperature region, while the phonon
entropy stabilizes the hexagonal phase thermodynamically in the
high-temperature region. The orthorhombic-to-hexagonal phase transition
temperature is 165 K, which is determined using the self-consistent
phonon calculations. We investigate the magnetocrystalline anisotropy energy
(MAE) using the self-consistent and non-self-consistent (force theorem)
calculations with the spin-orbit interaction (SOI) along with the Hubbard
correction. Then, we find that the orthorhombic phase has similar MAE, orbital
moment, and its anisotropy to the hexagonal phase when the self-consistent
calculation with the SOI is performed. Since the orthorhombic phase still gives
magnetic properties comparable to the experiments, the orthorhombic distortion
is potentially realized in the low-temperature region, which awaits
experimental exploration
Implementation strategies in phonopy and phono3py
Scientific simulation codes are public property sustained by the community.
Modern technology allows anyone to join scientific software projects, from
anywhere, remotely via the internet.
The phonopy and phono3py codes are widely used open source phonon calculation
codes. This review describes a collection of computational methods and
techniques as implemented in these codes and shows their implementation
strategies as a whole, aiming to be useful for the community. Some of the
techniques presented here are not limited to phonon calculations and may
therefore be useful in other area of condensed matter physics
Chemical Doping-Driven Giant Anomalous Hall and Nernst Conductivity in Magnetic Cubic Heusler Compounds
Chemical doping efficiently optimizes the physical properties of Heusler
compounds, especially their anomalous transport properties, including anomalous
Hall conductivity (AHC) and anomalous Nernst conductivity (ANC). This study
systematically investigates the effect of chemical doping on AHC and ANC in
1493 magnetic cubic Heusler compounds using high-throughput first-principles
calculations. Notable trends emerge in Co- and Rh-based compounds, where
chemical doping effectively enhances the AHC and ANC. Intriguingly, certain
doped candidates exhibit outstanding enhancement in AHCs and ANCs, such as
(CoNi)FeSn with considerable AHC and ANC values of
~S\,cm and ~A\,mK, respectively, and
(RhRu)MnIn with an AHC of ~S\,cm. In
particular, an extraordinary ANC of ~A\,mK is identified
exclusively in RhCoFeIn, nearly double the maximum value of
~A\,mK observed in the stoichiometric RhCoIn. A
comprehensive band structure analysis underscores that the notable enhancement
in ANC arises from the creation and modification of the energy-dependent nodal
lines through chemical doping. This mechanism generates a robust Berry
curvature, resulting in significant ANCs. These findings emphasize the pivotal
role of chemical doping in engineering high-performance materials, thereby
expanding the horizons of transport property optimization within Heusler
compounds.Comment: 18 pages, 8 figure