Atsushi Togo

First principles phonon calculations in materials science

Phonon plays essential roles in dynamical behaviors and thermal properties, which are central topics in fundamental issues of materials science. The importance of first principl...

First-principles calculations of the ferroelastic transition between rutile-type and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>CaCl</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>-type<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>SiO</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>at high pressures

The tetragonal to orthorhombic ferroelastic phase transition between rutile- and CaCl2-type SiO2 at high pressures is studied using first-principles calculations and the Landau ...

Distributions of phonon lifetimes in Brillouin zones

Lattice thermal conductivities of zincblende- and wurtzite-type compounds\nwith 33 combinations of elements are calculated with the single-mode\nrelaxation-time approximation an...

First-principles phonon calculations of thermal expansion in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Ti</mml:mtext></mml:mrow><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mtext>SiC</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Ti</mml:mtext></mml:mrow><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mtext>AlC</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>, and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Ti</mml:mtext></mml:mrow><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mtext>GeC</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>

Thermal properties of ternary carbides with composition Ti3SiC2, Ti3AlC2, and Ti3GeC2 were studied using the first-principles phonon calculations. The thermal expansions, the he...

Phonon-phonon interactions in transition metals

In this paper the phonon self energy produced by anharmonicity is calculated\nusing second order many body perturbation theory for all bcc, fcc and hcp\ntransition metals. The s...

Thermal physics of the lead chalcogenides PbS, PbSe, and PbTe from first principles

The lead chalcogenides represent an important family of functional materials,\nin particular due to the benchmark high-temperature thermoelectric performance\nof PbTe. A number ...

Evolution of crystal structures in metallic elements

Crystal structures of metals are often treated as dense packing of atomic spheres. Face-centered cubic and hexagonal close-packed structures are favored in many metals. Long-per...

High-pressure torsion of titanium at cryogenic and room temperatures: Grain size effect on allotropic phase transformations

Inversion Symmetry Breaking by Oxygen Octahedral Rotations in the Ruddlesden-Popper<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>Na</mml:mi><mml:mi>R</mml:mi><mml:msub><mml:mrow><mml:mi>TiO</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>Family

Rotations of oxygen octahedra are ubiquitous, but they cannot break inversion symmetry in simple perovskites. However, in a layered oxide structure, this is possible, as we demo...

Transition pathway of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">C</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>crystals under high pressures

The pressure-induced transitions from molecular to nonmolecular CO2 crystals are systematically investigated by using first-principles lattice dynamics calculations. Geometrical...

Neutron diffraction measurements and first-principles study of thermal motion of atoms in select<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi>M</mml:mi><mml:mrow><mml:mi>n</mml:mi><mml:mo>+</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msub><mml:mi>A</mml:mi><mml:msub><mml:mi>X</mml:mi><mml:mi>n</mml:mi></mml:msub></mml:mrow></mml:math>and binary<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>M</mml:mi><mml:mi>X</mml:mi></mml:mrow></mml:math>transition-metal carbide phases

Herein, we compare the thermal vibrations of atoms in select ternary carbides\nwith the formula Mn+1AXn ("MAX phases," M = Ti, Cr; A = Al, Si, Ge; X = C, N)\nas determined from ...

Phonon softening in paramagnetic bcc Fe and its relationship to the pressure-induced phase transition

Structural stability of paramagnetic (PM) body-centered cubic (bcc) Fe under\npressure is investigated based on first-principles phonon calculations. Spin\nconfigurations of the...

Ab initio ORTEP drawings: a case study of N-based molecular crystals with different chemical nature

The thermal motion of atoms and functional groups is a key characteristic of any molecular crystal, and such motion derived from scattering experiments is conveniently visualise...

Electronic structures of dynamically stable As<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow/><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>O<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow/><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>, Sb<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow/><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>O<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow/><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>, and Bi<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow/><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>O<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow/><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>crystal polymorphs

The relationships between the atomic arrangements, electronic structures, and energetics of three sesquioxides, As2O3, Sb2O3, and Bi2O3, are systematically investigated by first...

First principles study of thermal conductivity cross-over in nanostructured zinc-chalcogenides

Systematic first principles studies of zinc-chalcogenides have been performed to understand their thermal transport behaviour. We have applied the Boltzmann transport equation i...

Anisotropic phonon density of states in FePt nanoparticles with<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>L</mml:mi><mml:msub><mml:mn>1</mml:mn><mml:mn>0</mml:mn></mml:msub></mml:mrow></mml:math>structure

The phonon states of iron atoms in the easy-axis aligned $L{1}_{0}\text{-FePt}$ nanoparticles were investigated using $^{57}\text{F}\text{e}$ nuclear-resonant inelastic scatteri...