Ikutaro Hamada 교수

I propose a van der Waals density functional (vdW-DF) that improves upon the description of energetics and geometries of molecules, solids, and adsorption systems over the original vdW-DF. The functional is based on the nonlocal correlation for the second version of the vdW-DF [Lee et al., Phys. Rev. B 82, 081101(R) (2010)] and an exchange functional that recovers the second-order gradient expansion approximation in the slowly varying limit, while reproducing the large density gradient behavior

We present a comparative van der Waals density-functional (vdW-DF) study of graphene adsorbed on (111) surfaces of Ni, Cu, Pd, Ag, Au, and Pt, using the second version of vdW-DF (vdW-DF2) of Lee et al. [Phys. Rev. B 82, 081101(R) (2010)] and the exchange functional (C09) developed by Cooper [Phys. Rev. B 81, 161104(R) (2010)]. We show that the use of the vdW-DF2 correlation together with the C09 exchange yields the most satisfactory results: Adsorption geometries of graphene are in good agreemen

The van der Waals density functional (vdW-DF) was used to investigate the interaction of a water monomer with graphene. It was found that a variant of vdW-DF [Hamada and Otani, Phys. Rev. B 82, 153412 (2010)] predicts geometries and energetics of water on graphene which are in good agreement with those obtained using more elaborate random-phase approximation and quantum Monte Carlo approaches. Interfacial electronic structures were also analyzed in detail.

Periodic density functional theory was used to investigate the stability and electronic structures of precious-metal atoms in the vicinity of LaFe(1-x)M(x)O(3) (M = Pd, Rh, Pt) perovskite catalyst surfaces. It was found that the surface segregation of Pd and Pt is significantly stabilized by the introduction of O vacancies, whereas the solid-solution phase is favorable for Rh, suggesting an important role of O vacancies in the self-regeneration of Pd and Pt. On the basis of the results, we propo

Density-functional theory is utilized to study the energetics and vibrational properties of hydrogen on the Pt(111) surface in order to clarify the adsorption state of hydrogen on a Pt electrode in an electrochemical condition. Particular attention is paid to the Pt−H stretching frequency (νPt−H) of hydrogen on the atop site, which is often referred to as overpotentially deposited hydrogen and considered to be the reaction intermediate of the hydrogen evolution reaction. We investigate the origi

When modeling a surface/interface using a slab geometry that imposes the periodic boundary condition, there are spurious dipole and higher-order multipole interactions with the image slabs. Here, we show that the effective screening medium (ESM) method [M. Otani and O. Sugino, Phys. Rev. B 73, 115407 (2006)] can deal with such electrostatic issues rigorously in a slab calculation. After benchmark calculations for a hypothetical water layer, we show that there is an error in the total energy caus

Choosing the water bilayer/Rh(111) interface as an example, we study the interaction of water with a metal surface, by taking into account the van der Waals (vdW) interactions using the vdW density functional (vdW-DF). There are two types of water in a water bilayer on the substrate, namely, chemisorbed and physisorbed ones. We show that for a chemisorbed water molecule, vdW-DF results agree well with those obtained using the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation. Howev

We address the dispersion force in a ${\mathrm{C}}_{60}$/Au(111) interface using the van der Waals density functional with improved exchange [V. R. Cooper, Phys. Rev. B 81, 161104(R) (2010)] and nonlocal correlation [K. Lee, \'E. D. Murray,L. Kong, B. I. Lundqvist, and D. C. Langreth, Phys. Rev. B 82, 081101(R) (2010)]. We found that the adsorption is solely attributed to the nonlocal correlation, i.e., the van der Waals (vdW) forces, and the correct account of vdW attraction between ${\mathrm{C

Density functional theory with the van der Waals density functional (vdW-DF) is used to calculate equilibrium crystal structure, binding energy, and bulk modulus of ice Ih. It is found that although it overestimates the equilibrium volume, vdW-DF predicts accurate binding energy of ice Ih, as compared with high level quantum chemistry calculations and experiment. Inclusion of the nonlocal correlation, i.e., van der Waals interaction, leads to an overall improvement over the standard generalized