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講演 １
『Development of anharmonic vibrational analysis methods for soft molecular systems』
講演者
八木 清専任研究員 (理化学研究所 杉田理論分子科学研究室)
講演要旨
Recent developments to generate an anharmonic potential energy surface (PES) using electronic structure calculations and to solve the vibrational Schrödinger equation have made feasible to compute the vibrational spectrum of a “single” polyatomic molecule with high accuracy. However, computing the spectrum of complex molecular systems remains a challenge due to the effect of environment and multiple conformers that contribute to the spectrum. We have developed a QM/MM method to incorporate the environment in the PES, and a weight averaged approach to account for multiple conformers. As pilot applications, I will present the infrared spectrum of phosphate ions in solution and amorphous phase of polyamide material interacting with water computed by our approach.
講演 ２
『Identifying time scales for violation/preservation of Stokes-Einstein relation in supercooled water』
講演者
金 鋼准教授 (大阪大学大学院基礎工学研究科)
講演要旨
The violation of Stokes-Einstein (SE) relation D∼(η/T)^−1 between shear viscosity η and diffusion constant D at temperature Tis of great importance for characterizing anomalous dynamics of supercooled water.
Determining which time scales play key roles in the SE violation remains elusive without the measurement of η. Here we provide comprehensive simulation results of the dynamic properties involving η and D in TIP4P/2005 supercooled water. This enabled the thorough identification of the appropriate time scales for SE relation Dη/T. In particular, it is demonstrated that the temperature dependence of various time scales associated with structural relaxation, hydrogen-bond breakage, stress relaxation, and dynamic heterogeneities can be definitely classified into just two classes. That is, we propose the generalized SE relations which exhibit "violation" or "preservation". The classification depends on the examined time scales which are coupled or decoupled with the diffusion.
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