Y. A. Ran

Oct 23, 2024 | pubs.aip.org | Los Alamos |Jinzhe Zeng |Y. A. Ran

As plutonium ages, several physical changes occur, including a reduction in density, changes in isotopic composition, nucleation and growth of helium bubbles, accumulation of deformation energy due to lattice defects and Frenkel pairs, an increase in yield stress, and a stiffening of the bulk modulus. These mechanisms have been the subject of much research during the past 20 years.

Oct 23, 2024 | pubs.aip.org | Jinzhe Zeng |Y. A. Ran

Unlike one-dimensional polymers, the theoretical framework on the behaviors of two-dimensional (2D) polymers is far from completeness. In this study, we model single-layer flexible 2D polymers of different sizes and examine their scaling behaviors in solution, represented by R ∼ Lν, where R is the radius of gyration and L is the side length of a 2D polymer. We find that the scaling exponent ν is 0.96 for a good solvent and 0.64 for under poor solvent condition.

Oct 22, 2024 | pubs.aip.org | Leninskie Gory |Jinzhe Zeng |Y. A. Ran

We describe the new method that can be useful for calculation of the excitation dynamics in large molecular arrays that can be split into compartments with weak exciton coupling between them. In this method, the dynamics within each compartment is evaluated nonperturbatively using hierarchical equations of motion (HEOM), whereas transfers between the exciton states belonging to different compartments are treated by the generalized Förster (gF) theory.

Oct 18, 2024 | pubs.aip.org | Y. A. Ran |Jinzhe Zeng

The dynamics of molecular excitonic systems are complicated by a competition between electronic coupling (which drives delocalization) and vibrational-electronic (vibronic) interactions (which tend to encourage electronic localization). A particular challenge of molecular systems is that they typically possess a large number of independent vibrations, with frequencies often spanning the entire spectrum of relevant electronic energy gaps.