SearcharxivSearch

arXiv subjects

Riichi Kuwahara

Publications and source records attributed to Riichi Kuwahara.

2 recordsLinked to original sources

Molecular dynamics simulation for cross-linking processes and material properties of epoxy resins with the first principle calculation combined with global reaction route mapping algorithms

Herein, epoxy resin is cured by coupling quantum chemical (QC) calculations with molecular dynamics (MD) simulations that enable parameter-free prediction of material characteristics. A polymer network is formed by the reaction between base resin and curing agent. The reaction uses activation energy and heat of formation data obtained by first-principle calculations coupled with global reaction route mapping (GRRM) algorithms. Density, glass transition temperature, Young's modulus, and curing conversion is used to validate the procedure. Experimental and simulation results indicate that base resin with multi-functional reaction groups increases glass-transition temperature and Young's modulus because of cross-linked formations at the molecular scale.

cond-mat.soft

GWΓ + Bethe-Salpeter equation approach for photoabsorption spectra: Importance of self-consistent GWΓ calculations in small atomic systems

The self-consistent GWΓ method satisfies the Ward-Takahashi identity (i.e., the gauge invariance or the local charge continuity) for arbitrary energy ($ω$) and momentum ($\bf q$) transfers. Its self-consistent first-principles treatment of the vertex $Γ=Γ_v$ or $Γ_W$ is possible to first order in the bare ($v$) or dynamically-screened ($W$) Coulomb interaction. It is developed within a linearized scheme and combined with the Bethe-Salpeter equation (BSE) to accurately calculate photoabsorption spectra (PAS) and photoemission (or inverse photoemission) spectra (PES) simultaneously. The method greatly improves the PAS of Na, Na$_3$, B$_2$, and C$_2$H$_2$ calculated using the standard one-shot $G_0W_0$ + BSE method that results in significantly redshifted PAS by 0.8-3.1 eV, although the PES are well reproduced already in $G_0W_0$.

cond-mat.other