Embedded Files
Time-Series Spectroscopy Analysis
Time-Series Spectroscopy Analysis
Calculating accurate spectral densities is important for excitation energy transfer dynamics in multichromophore systems as well as for condensed-phase linear and nonlinear spectroscopy. Measuring the properties of these fluctuations is therefore essential in light of potential optoelectronic applications. Here we apply two-dimensional electronic spectroscopy (2DES) to probe the timescale and amplitude of the electronic gap correlations in photoactive yellow protein (PYP) in water via homogeneous lineshape dynamics.
High-Performance OLED Material Identifier
High-Performance OLED Material Identifier
This materials development strategy takes into consideration the full multilayer OLED device, rather than just individual components. In addition to introducing this protocol, an evolutionary method, a genetic algorithm (GA), is evaluated in detail to increase its efficiency in searching through a library of 30 million organic compounds. On the basis of the optimization of the variety of GA parameters and selection methods, an exponential ranking selection protocol with a high mutation rate is found to be the preferred method for quickly identifying the top-performing molecules within the large chemical space. This search through OLED materials space shows that the pyridine-based central core with acridine-based fragments are good target host molecules for common electrode materials. Additionally, weak electron-donating groups, such as naphthalene- and xylene-based fragments, appear often in the optimal electron-transport layer materials. Triphenylamine- and acridine-based fragments, due to their strong electron-donating character, were found to be good candidates for the hole-transport layer.
Anharmonic Frequency Calculations (VCI)
Anharmonic Frequency Calculations (VCI)
Vibrational anharmonicity contributes significantly to the energies and entropies coming from atomistic simulation. In order to capture these effects, quantum chemical methods have been proposed to go beyond the harmonic approximation and describe the physically important anharmonicities and anharmonic couplings between modes. Due to the immense expense of computing fully anharmonic energy levels, however, approximations must be made to the vibrational wave functions. Our approach to address these challenges provides a tunable windowing strategy to optimize of local modes and perform vibrational configuration interaction within these windows. This allows the higher-order mode-mode couplings in the vibrational potential energy surfaces to be neglected, ultimately resulting in dramatically lower costs. To demonstrate the applicability and transferability of the proposed method, we will show a series of benchmarks for the vibrational entropy and anharmonic vibrational spectra of organic molecules, and that the calculated results are in a good agreement with the experimental spectra. Finally, comparisons of approximated total vibrational energies and entropies to the harmonic and exact limits will numerically validate that high accuracy can be maintained, even with substantially reduced computational costs.
Molecular Dynamic Simulations and Time-Series Analysis
Molecular Dynamic Simulations and Time-Series Analysis
A nano Ag5 cluster tip probing the vertical transfer of CO(ads) adsorbed on a Ag(110) surface has been investigated with simulated inelastic electron tunneling spectroscopy (IETS) generated by combining DFT-based molecular dynamic simulations with a Fourier transform of auto-correlation function of the derivative of local density of states (FT-ACF-dLDOS). It is found that tunneling conductance generated based on the trajectories of LDOS is significantly increased as a nano Ag5 cluster tip is introduced and their vibrational amplitudes of low-frequency modes are enhanced in IETS. In addition, the IETS shows the doublet feature in the regions of low-frequency mode, i.e. frustrated-rotation, and high-frequency mode, i.e. C–O stretching, respectively, due to the change of geometry of CO(ads) leading to the transfer of CO(ads) adsorbed on the Ag(110) surface to a nano Ag5 cluster tip. Furthermore, an anharmonic coupling between frustrated-rotation and C–O stretching mode is investigated by using time-resolved IETS analysis. Finally, the key issue regarding the activation of low-frequency modes by a nano Ag5 cluster tip to cause the transfer of CO(ads) adsorbed on Ag(110) surface is addressed.
Page updated
Report abuse