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The steepest-entropy-ascent quantum thermodynamic (SEAQT) framework was used to calculate the stability of a collection of point defects in 2D PtSe$_2$ and predict the kinetics with which defects rearrange during thermal annealing. The framework provides a non-equilibrium, ensemble-based framework with a self-consistent link between mechanics (both quantum and classical) and thermodynamics. It employs an equation of motion derived from the principle of steepest entropy ascent (maximum entropy production) to predict the time evolution of a set of occupation probabilities that define the states of a system undergoing a non-equilibrium process. The system is described by a degenerate energy landscape of eigenvalues, and the entropy is found from the occupation probabilities and the eigenlevel degeneracies. Scanning tunneling microscopy was used to identify the structure and distribution of point defects observed experimentally in a 2D PtSe$_2$ film. A catalog of observed defects included six unique point defects (vacancies and anti-site defects on Pt and Se sublattices) and twenty combinations of multiple point defects in close proximity. The defect energies were estimated with density functional theory (DFT), while the degeneracies, or density of states, for the 2D film with all possible combinations or arrangements of cataloged defects was constructed using a non-Markovian Monte-Carlo approach (i.e., the Replica-Exchange-Wang-Landau algorithm) with a q-state Potts model. The energy landscape and associated degeneracies were determined for a 2D PtSe$_2$ film two molecules thick and $30 \times 30$ unit cells in area (total of 5400 atoms). The SEAQT equation of motion was applied to the energy landscape to determine how an arbitrary density and arrangement of the six defect types evolve during annealing., Comment: 19 pages, 11 pdf and png figures, uses revtex4-2. This paper employs the steepest-entropy ascent (or maximum entropy production) principle to predict the migration kinetics and stable equilibrium arrangement of point defects in a two-dimensional material (PtSe2)

The kinetics of ordering and concurrent ordering and clustering is analyzed with an equation of motion initially developed to account for dissipative processes in quantum systems. A simplified energy eigenstructure, or pseudo-eigenstructure, is constructed from a static concentration wave method to describe the configuration-dependent energy for atomic ordering and clustering in a binary alloy. This pseudo-eigenstructure is used in conjunction with an equation of motion that follows steepest entropy ascent to calculate the kinetic path that leads to ordering and clustering in a series of hypothetical alloys. By adjusting the thermodynamic solution parameters, it is demonstrated that the model can predict the stable equilibrium state as well as the unique thermodynamic path and kinetics of continuous/discontinuous ordering and concurrent processes of simultaneous ordering and phase separation., Comment: 10 pages

The new series of recently synthesized chromophores 2 - 6 in which a positively charged N-alkylpyridinium acceptor and a negatively charged dicyanomethanide donor are spaced by thiophene-based and/or ethylenic bridging units show dramatically enhanced first molecular hyperpolarizabilities (μβ as high as 27000 × 10−48esu), in comparison with some of the best recently reported neutral systems 7 and 8.