Computer simulations from first principles enable us to investigate properties and behavior of materials beyond the limits of experiments. Our main subject is to develop and apply such methods to explain the physics of materials, to predict material properties, and to create new materials.
 Development of the transcorrelated method for condensed matter
The transcorrelated (TC) method, initially proposed by S. F. Boys and N.
C. Handy more than 40 years ago but forgotten until recently, is a wave
function theory for firstprinciples electronic structure calculation with
explicitly correlated wave functions. We noticed its conceptual and practical
importance and have been trying to establish the method for an alternative
of the density functional theory for years. In 2006, we reported the first
application of the TC method to the band structure calculation, but there
was a severe problem of the computational cost. After 2012, we developed
new algorithms to speed up the calculation drastically and realized its
application to various materials and extended the method for the calculation
of electronic excitation spectra also. We showed that the electronic band
structure of ZnO is reproduced best among the firstprinciples methods
reported so far [1].
 Development of the firstprinciples simulation of the thermal properties of crystals.
For the simulation of the thermal properties of crystals, a precise calculation
of the anharmonic phonon effect is necessary. A problem there is that the
spatiotemporal scale of phonon properties is diverse. So it is not easy
to simulate them by the simple application of the firstprinciples simulation.
We developed a method to combine firstprinciples molecular dynamics with
socalled sparse modeling, and established reliable calculation of the
thermal conductivity of crystals [2]. We also introduced the selfconsistent
phonon approach to calculate soft phonon modes of hightemperature/highsymmetry
phases realized by the thermal fluctuation of atoms with a modest computational
cost. We applied these methods to clarify the mechanism of extremely low
thermal conductivity in a clathrate [3]. Our code (ALAMODE) is open for
the public and used by researchers in the academy and also in industry.
 Development of the Superconducting DFT code and its application to hydrogen sulfide at high pressure
In 2015, hydrogen sulfide made a record of the superconducting transition
temperature (Tc) at high pressure. The surprisingly high Tc above 200K
is explained by the phonon mechanism, on which we have contributed by the
world's first calculation of the accurate Tc with the superconducting density
functional theory (SCDFT) [4]. In this study, we used an inhouse SCDFT
code we developed, for which we had made an efficient method for the Brillouinzone
integration to improve the convergence of the calculation.
 Development of the data assimilation method to predict crystal structures
Theoretical prediction of crystal structures from its chemical composition
and physical conditions has been a longstanding problem of physical sciences.
Although there have been so many successful researches on the structural
search algorithms, the number of atoms in the unit cell reachable with
these algorithms is limited. We made a method to assimilate powder diffraction
data in the structure simulation [5]. We showed the search of complicated
crystal structures are highly accelerated even if the diffraction data
is incomplete due to the experimental constraints or the problem of the
quality of the sample. The method will support structure determination
in, for example, highpressure experiments or materials development.
 Nonthermal laser ablation of metals by a femtosecond laser
Femtosecond laser irradiation on a metal surface changes the electron subsystem
and causes ablation without apparent thermal damage to the surrounding
area. We often call this phenomenon a nonthermal ablation, but its physical
mechanism is unclear. Based on the firstprinciples calculation of an electronically
hightemperature system, we proposed the electronic entropydriven mechanism
for the ¡Ænonthermal¡Ç ablation. We developed a simple simulation model
for ablation and succeeded in the reproduction of the ablation depth of
Copper as a function of the laserfluence [6].
[1] M. Ochi, et al., Correlated Band Structure of a Transition Metal Oxide
ZnO Obtained from a ManyBody Wave Function Theory, Phys. Rev. Lett. 118,
026402 (2017).
[2] T. Tadano, et al., Anharmonic force constants extracted from firstprinciples
molecular dynamics: applications to heat transfer simulations, J. Phys.:
Condens. Matter 26, 225402 (2014).
[3] T. Tadano, et al., Impact of Rattlers on Thermal Conductivity of a
Thermoelectric Clathrate: A FirstPrinciples Study, Phys. Rev. Lett. 114,
095501 (2015).
[4] R. Akashi et al., Firstprinciples study of the pressure and crystalstructure
dependences of the superconducting transition temperature in compressed
sulfur hydrides, Phys. Rev. B 91, 224513 (2015).
[5] N. Tsujimoto, D. Adachi, R. Akashi, S. Todo, and S. Tsuneyuki, Crystal structure prediction supported by incomplete experimental data, Phys. Rev. Materials 2, 053801 (2018).
[6] Y. Tanaka and S. Tsuneyuki, Possible electronic entropydriven mechanism
for nonthermal ablation of metals, Appl. Phys. Express 11, 046701 (2018).

Methods for firstprinciples electronic structure calculation
 Yuansheng Zhao Ryuhei Sato and Shinji Tsuneyuki, Accelerating simulated annealing of glassy materials with data assimilation, J. NonCryst. Solids 600, 122028 (2022).
 Cristian M. Le, Ryosuke Akashi, Shinji Tsuneyuki, The missing quantum number
of the Floquet states, Phys. Rev. A 105, 052213 (2022)
 D. Adachi, N. Tsujimoto, R. Akashi, S. Todo and S. Tsuneyuki, Search for common minima in joint optimization of multiple cost functions, Comput. Phys. Commun. 241, 9297 (2019)
 N. Tsujimoto, D. Adachi, R. Akashi, S. Todo, and S. Tsuneyuki, Crystal
structure prediction supported by incomplete experimental data, Phys. Rev. Materials 2, 053801 (2018).
 S. Yamada, F. Shimojo, R. Akashi, and S. Tsuneyuki, Efficient method for
calculating spatially extended electronic states of large systems with
a divideandconquer approach, Phys. Rev. B 95, 045106 (2017).
 M. Ochi, R. Arita, and S. Tsuneyuki, Correlated Band Structure of a Transition
Metal Oxide ZnO Obtained from a ManyBody Wave Function Theory, Phys. Rev. Lett. 118, 026402 (2017).
 M. Ochi, Y. Yamamoto, R. Arita and S. Tsuneyuki, Iterative diagonalization
of the nonHermitian transcorrelated Hamiltonian using a planewave basis
set: Application to spelectron systems with deep core state, J. Chem. Phys. 144, 4109 (2016).
 M. Ochi and S. Tsuneyuki, Secondorder MollerPlesset perturbation theory
for the transcorrelated Hamiltonian applied to solidstate calculations,
Chem. Phys. Lett. 621, 177183 (2015).
 M. Ochi, K.Sodeyama and S. Tsuneyuki, Optimization of the Jastrow factor using the randomphase approximation and a similaritytransformed Hamiltonian: Application to bandstructure calculation for some semiconductors and insulators, J. Chem. Phys. 140, 074112112 (2014).
 M. Ochi and S. Tsuneyuki, Optical Absorption Spectra Calculated from a
FirstPrinciples Wave Function Theory for Solids: Transcorrelated Method
Combined with Configuration Interaction Singles, J. Chem. Theo. Comp. 10, 40984103 (2014).
 M. Kawamura, Y. Gohda and S. Tsuneyuki, Improved tetrahedron method for
the Brillouinzone integration applicable to response functions, Phys. Rev. B89, 094515 (2014).
 T. Kobori, K. Sodeyama, T. Otsuka, Y. Tateyama and S. Tsuneyuki, Trimer
Effects in Fragment Molecular OrbitalLinear Combination of Molecular Orbitals
Calculation of OneElectron Orbitals for Biomolecules, J. Chem. Phys., 139, 094113 (2013).
 M. Ochi, K. Sodeyama, R. Sakuma and S. Tsuneyuki, Efficient algorithm of
the transcorrelated method for periodic systems, J. Chem. Phys. 136, 094108(2012).
Superconductivity
 M. Kawamura, R. Akashi and S. Tsuneyuki, Anisotropic superconducting gaps
in YNi2B2C: A firstprinciples investigation, Phys. Rev. B 95, 4506 (2017).
 R. Akashi, W. Sano, R. Arita, and S. Tsuneyuki, Possible ¡ÈMagneli¡É Phases
and SelfAlloying in the Superconducting Sulfur Hydride, Phys. Rev. Lett. 117, 075503 (2016). Editor's Suggestion
 R. Akashi, M. Kawamura, S. Tsuneyuki, Y. Nomura, R. Arita, Firstprinciples
study of the pressure and crystalstructure dependences of the superconducting
transition temperature in compressed sulfur hydrides, Phys. Rev. B 91, 224513 (2015).
Thermal properties
 M. Ohnishi, T. Tadano, S. Tsuneyuki, J. Shiomi, Anharmonic phonon renormalization
and thermal transport in the typeI Ba8Ga16Sn30 clathrate from first principles,
Phys. Rev. B 106, 024303 (2022).
 Y. Oba, T. Tadano, R. Akashi and S. Tsuneyuki, Firstprinciples study of
phonon anharmonicity and negative thermal expansion in ScF_{3}, Phys. Rev. Materials 3, 033601111 (2019).
 T. Tadano and S. Tsuneyuki, Quartic Anharmonicity of Rattlers and Its Effect
on Lattice Thermal Conductivity of Clathrates from First Principles, Phys. Rev. Lett., 120, 10590116 (2018).
 T. Tadano and S. Tsuneyuki, FirstPrinciples Lattice Dynamics Method for
Strongly Anharmonic Crystals, J. Phys. Soc. Japan 87, 041015 (2018).
 T. Tadano and S. Tsuneyuki, Selfconsistent phonon calculations of lattice
dynamical properties in cubic SrTiO_{3} with firstprinciples anharmonic force constatns, Phys Rev. B 92, 054301 (2015).
 T. Tadano, Y. Gohda, and S. Tsuneyuki, Impact of Rattlers on Thermal Conductivity
of a Thermoelectric Clathrate: A FirstPrinciples Study, Phys. Rev. Lett. 114, 095501 (2015).
 T. Tadano, Y. Gohda, and S. Tsuneyuki, Anharmonic force constants extracted
from firstprinciples molecular dynamics: applications to heat transfer
simulations, J. Phys.: Condens. Matter 26, 225402 (2014).
Photoexcitation and laser ablation
 Cristian M. Le, Ryosuke Akashi, Shinji Tsuneyuki, The missing quantum number
of the Floquet states, Phys. Rev. A 105, 052213 (2022)
 H. Katow, R. Akashi, Y. Miyamoto, S. Tsuneyuki, First Principles Study
of the Optical Dipole Trap for TwoDimensional Excitons in Graphane, Phys. Rev. Lett. 129, 047401 (2022).
 Y. Tanaka and S. Tsuneyuki, Possible electronic entropydriven mechanism
for nonthermal ablation of metals, Appl. Phys. Express 11, 04670114 (2018) (Spotlights 2018)
 H. Katow, J. Usukura, R. Akashi, K. Varga and S. Tsuneyuki, Numerical investigation of triexciton stabilization in diamond with multiple valleys and bands, Phys. Rev. B95, 125205 (2017).
Dielectric materials and impurities
 N. Sato, R. Akashi, and S. Tsuneyuki, Universal twodimensional characteristics in perovskitetype oxyhydrides ATiO2H (A = Li, Na, K, Rb, Cs) , J. Chem. Phys., 147,034507(2017) .
 N. Sato and S. Tsuneyuki, Perovskitetype oxyhydride with a twodimensional
electron system: Firstprinciples prediction of KTiO_{2}H, Appl. Phys. Lett. 109, 172903 (2016).
 Y. Iwazaki, Y. Gohda and S. Tsuneyuki, Diversity of hydrogen configuration
and its roles in SrTiO_{3delta}, APL Mat. 2, 012103 (2014).
 Y. Iwazaki, T. Suzuki, Y. Mizuno and S. Tsuneyuki, Dopinginduced phase
transitions in ferroelectric BaTiO3 from firstprinciples calculations,
Phys. Rev. B86, 214103(2012).
Magnetic materials
 Yuki K. Wakabayashi, Yoshiharu Krockenberger, Naoto Tsujimoto, Tommy Boykin,
Shinji Tsuneyuki, Yoshitaka Taniyasu and Hideki Yamamoto, Ferromagnetism
above 1000 K in a highly cationordered doubleperovskite insulator Sr_{3}OsO_{6}, Nature Communications 10, 535 (2019).
 Y. Tatetsu, S. Tsuneyuki, and Y. Gohda, Firstprinciples study on substitution effects in Nd_{2}(Fe, X)_{14}B, Materialia 4, 388394 (2018).
 Y. Tatetsu, S. Tsuneyuki, and Y. Gohda, FirstPrinciples Study of the Role
of Cu in Improving the Coercivity of NdFeB Permanent Magnets, Phys. Rev. Applied 6, 064029 (2016).
 Z. Torbatian, T. Ozaki, S. Tsuneyuki and Y. Gohda, Strain effect on the magnetic anisotropy of Y2Fe14B examined by firstprinciples calculations, Appl. Phys. Lett. 104, 24240314 (2014).
Surface and Interface
 Y. Gohda, Y. Tatetsu, and S. Tsuneyuki, Electron theory on grainboundary
structures and local magnetic properties of neodymium magnets, Mater. Trans., 59, 332 (2018).
 Y. Ando, Y. Gohda and S. Tsuneyuki, Dependence of the Schottky barrier
on the work function at metal/SiON/SiC(0001) interfaces identified by firstprinciples
calculations, Surf. Sci. 606, 1501(2012)
 Y. Ando, Y. gohda and S. Tsuneyuki, Ab initio molecular dynamics study
of the Helmholtz layer formed on solid?liquid interfaces and its capacitance,
Chem. Phys. Lett. 556, 912 (2012).
 Y. Gohda and S. Tsuneyuki, Structural Phase Transition of Graphene Caused by GaN Epitaxy, Appl. Phys. Lett. 100, 05311114 (2012).
 Y. Gohda and S. Tsuneyuki, Twodimensional intrinsic ferromagnetism at
nitrideboride interfaces, Phys. Rev. Lett. 106, 047201 (2011).
