Taisuke Ozaki

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We present a DFT study for the adsorption of single Pt atom and Pt clusters on graphene surface and carbon nanotube. Adsorption of a Pt atom shows a heavy dependence of binding energy on the graphene curvature. The adsorbed Pt atoms tend to form clusters, than to disperse on the graphene surface. The Pt–Pt bond length and the charge transfer from Pt(More)
To investigate the electronic structure and magnetic properties of manganese oxide clusters, we carried out first-principles electronic structure calculations for small MnO clusters. Among various structural and magnetic configurations of the clusters, the bulklike [111]-antiferromagnetic ordering is found to be favored energetically, while the surface(More)
With tens of petaflops supercomputers already in operation and exaflops machines expected to appear within the next 10 years, efficient parallel computational methods are required to take advantage of such extreme-scale machines. In this paper, we present a three-dimensional domain decomposition scheme for enabling large-scale electronic calculations based(More)
The fast Fourier transform (FFT) is undoubtedly an essential primitive that has been applied in various fields of science and engineering. In this paper, we present a decomposition method for parallelization of multi-dimensional FFTs with smallest communication amount for all ranges of the number of processes compared to previously proposed methods. This is(More)
A new O(N) algorithm based on a recursion method, in which the computational effort is proportional to the number of atoms N , is presented for calculating the inverse of an overlap matrix which is needed in electronic structure calculations with the the non-orthogonal localized basis set. This efficient inverting method can be incorporated in several O(N)(More)
A numerical method to calculate the four-center electron-repulsion integrals for strictly localized pseudoatomic orbital basis sets has been developed. Compared to the conventional Gaussian expansion method, this method has an advantage in the ease of combination with O(N) density functional calculations. Additional mathematical derivations are also(More)
We propose a new method for the numerical evaluation of the spherical Bessel transform. A formula is derived for the transform by using an integral representation of the spherical Bessel function and by changing the integration variable. The resultant algorithm consists of a set of the Fourier transforms and numerical integrations over a linearly spaced(More)
The fast Fourier transform (FFT) is a primitive kernel in numerous fields of science and engineering. OpenFFT is an open-source parallel package for 3-D FFTs, built on a communication-optimal domain decomposition method for achieving minimal volume of communication. In this paper, we analyze, model, and tune the performance of OpenFFT, paying a particular(More)
A method for large-scale first-principles molecular dynamics (MD) simulations on electrochemical systems has been developed by combining the effective screening medium (ESM) method with O(N) density functional theory (DFT). This implementation has been significantly simplified by the introduction of neutral atom potentials, which minimizes the modifications(More)
We present a decomposition method for the parallelization of multi-dimensional FFTs with two distinguishing features: adaptive decomposition and transpose order awareness for achieving minimal communication volume. Based on a row-wise decomposition that translates the multi-dimensional data into one-dimensional data for equally allocating to the processes,(More)