Exploring a free energy landscape of frustrated system by means of multi-dimensional spectroscopes

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The free energy landscape (FEL) is the conformational substates of the free energy as a function of macroscopic variables, which has been widely used to characterize the dynamical behavior of frustrated systems such as glasses and proteins. The aim of this research is to clarify some of postulation used to describe the dynamics of a frustrated system by exploring a possibility to measure the FEL directly by optical means. For this purpose, we consider a system consists of dipoles and employ a simple model to reduce the degrees of freedom. We calculated the FEL at various temperatures by generating all possible states and studied the dynamics of dipoles on the FEL by constructing the master equation for all states. For temperatures higher than the energy scale of dipole-dipole interactions. The free energy landscapes have quadratic shape. When the temperature drops, small notched structures appear on the free energy profiles because of the frustrated interactions among dipoles. From thi … More s approach, the new insight for electron transfer problem was obtained below the glass transition temperature, where the Marcus theory breaks down. The sensitivity of multidimensional spectroscopy is fully used to characterize the dynamics upon different FEL. Here, we calculated two-dimensional signals corresponding to infrared, far IR or THz spectroscopy defined by the four-body correlation functions of dipole operators. While the linear absorption signals decay in time in a similar manner regardless of the FEL profiles, the 2D signals exhibit prominent differences in those profiles. This indicates that, we may differentiate the profiles of FEL by changing two-time valuables involved in 2D spectroscopy. We also developed an efficient algorithm to study the dynamics of molecules on mulitidimensional spectroscopy from molecular dynamics simulation approach, which hybridizes the existing equilibrium and nonequilibrium methods of calculating multidimensional spectroscopy. As an application of this simulation method, we calculated two-dimensional Raman spectrum of various molecular liquids. Less