Superconducting high pressure phase of germane (2008)
Gao, Guoying, Oganov, Artem R., Bergara, Aitor, Martinez-Canales, Miguel, Cui, Tian, Iitaka, Toshiaki, ...
4 pages, 3 figures.-- PACS nrs.: 74.70.Ad, 74.10.+v, 74.25.Jb, 74.62.Fj.
Linear scaling calculation of a n-type GaAs quantum dot (2007)
Nomura, Shintaro, Iitaka, Toshiaki
A linear scale method for calculating electronic properties of large and complex systems is introduced within a local density approximation. The method is based on the Chebyshev polynomial expansion...
Hamada, Tsuyoshi, Iitaka, Toshiaki
We present an algorithm named "Chamomile Scheme". The scheme is fully optimized for calculating gravitational interactions on the latest programmable Graphics Processing Unit (GPU), NVIDIA...
Pressure-induced isostructural phase transition of metal-doped silicon clathrates (2006)
We propose an atomistic model for the pressure-induced isostructural phase transition of metal-doped silicon clathrates, Ba8Si46 and K8Si46, that has been observed at 14 GPa and 23 GPa, respectively....
太陽系外生命の第一原理計算をめざして : メタンハイドレート新高圧相など (2006)
1章 コンピュータシミュレーションが拓く水系物質研究のフロンティア
Temperature dependence of ESR intensity for the nanoscale molecular magnet V15 (2005)
Machida, Manabu, Iitaka, Toshiaki, Miyashita, Seiji
The electron spin resonance (ESR) of nanoscale molecular magnet ${\rm V}_{15}$ is studied. Since the Hamiltonian of ${\rm V}_{15}$ has a large Hilbert space and numerical calculations of the ESR...
Random phase vector for calculating the trace of a large matrix (2004)
Iitaka, Toshiaki, Ebisuzaki, Toshikazu
We derive an estimate of statistical error in calculating the trace of a large matrix by using random vector, and show that {\em random phase vector} gives the results with the smallest statistical...
Methane Hydrate under High Pressure: Searching for Centering of Hydrogen Bonds (2003)
Iitaka, Toshiaki, Ebisuzaki, Toshikazu
The structural, electronic, and spectroscopic properties of a high-pressure phase of methane hydrate (MH-III) are studied by first principles electronic structure calculations. A detailed analysis of...
Iitaka, Toshiaki, Ebisuzaki, Toshikazu
We introduce an efficient and numerically stable method for calculating linear response functions $\chi(\vec{q},\omega)$ of quantum systems at finite temperatures. The method is a combination of...
First Principles Calculation of Elastic Properties of Solid Argon at High Pressures (2001)
Iitaka, Toshiaki, Ebisuzaki, Toshikazu
The density and the elastic stiffness coefficients of fcc solid argon at high pressures from 1 GPa up to 80 GPa are computed by first-principles pseudopotential method with plane-wave basis set and...
Calculating response functions in time domain with non-orthonormal basis sets (2000)
Iitaka, Toshiaki, Ebisuzaki, Toshikazu
We extend the recently proposed order-N algorithms (cond-mat/9703224) for calculating linear- and nonlinear-response functions in time domain to the systems described by nonorthonormal basis sets.
Non-degenerate Two Photon Absorption Spectra of Si Nanocrystallites (1999)
Iitaka, Toshiaki, Ebisuzaki, Toshikazu
We propose an efficient linear-scaling time-dependent method for calculating nonlinear response function, and study the size effects in non-degenerate two photon absorption spectra of Si...
Computing the real-time Green's Functions of large Hamiltonian matrices (1998)
A numerical method is developed for calculating the real time Green's functions of very large sparse Hamiltonian matrices, which exploits the numerical solution of the inhomogeneous time-dependent...
Correlation functions for time-dependent calculation of linear-response functions (1997)
We emphasize the importance of choosing an appropriate correlation function to reduce numerical errors in calculating the linear-response function as a Fourier transformation of a time-dependent...
Iitaka, Toshiaki, Nomura, Shintaro, Hirayama, Hideki, Zhao, Xinwei, Aoyagi, Yoshinobu, Sugano, Takuo
An O(N) algorithm is proposed for calculating linear response functions of non-interacting electrons in arbitray potential. This algorithm is based on numerical solution of the time-dependent...