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Surface-facilitated, front-propagated softening of glassy materials is now a well-known phenomenon, which is common to stable vapor deposited glasses. As we demonstrate in our recent communication, this softening pathway is not unique to vapor-deposited vitreous phases and can be observed in ordinary melt-cooled glasses in the limit of high heating rates [Cubeta et al., J. Chem. Phys. 147(7), 071101 (2017)]. Expanding on this preliminary report, we use our thin-wire, quasi-adiabatic fast scanning calorimetry technique to investigate softening kinetics of micrometer scale, viscous liquid methylbenzene, and 2-propanol films, which are fully equilibrated at distinct temperatures near the compounds’ standard glass hardening transition ranges. Heating of each sample with rates in excess of 105 K·s−1 results in softening kinetics that are well approximated by an Arrhenius temperature function. Remarkably, the apparent activation energy barriers to non-equilibrium, front-propagated softening matches the barriers to near-equilibrium self-diffusivity at the samples’ initial temperatures. Furthermore, our analysis also shows an exceptionally strong correlation between the high temperature softening rate and the self-diffusion coefficients at low initial temperatures. Finally, our front softening velocities are also strongly dependent on the samples’ initial states, much more so than previously observed. Based on these results, we propose an extended Wilson-Frenkel model of non-equilibrium phase transformations as a general theoretical framework to describe front propagated softening in glassy materials.Surface-facilitated, front-propagated softening of glassy materials is now a well-known phenomenon, which is common to stable vapor deposited glasses. As we demonstrate in our recent communication, this softening pathway is not unique to vapor-deposited vitreous phases and can be observed in ordinary melt-cooled glasses in the limit of high heating rates [Cubeta et al., J. Chem. Phys. 147(7), 071101 (2017)]. Expanding on this preliminary report, we use our thin-wire, quasi-adiabatic fast scanning calorimetry technique to investigate softening kinetics of micrometer scale, viscous liquid methylbenzene, and 2-propanol films, which are fully equilibrated at distinct temperatures near the compounds’ standard glass hardening transition ranges. Heating of each sample with rates in excess of 105 K·s−1 results in softening kinetics that are well approximated by an Arrhenius temperature function. Remarkably, the apparent activation energy barriers to non-equilibrium, front-propagated softening matches the barriers...

We report the observation and assignments of several series of transitions in CH2DOH, including a new and intense series of Q-branch c-type transitions between the e1 and o1 torsional substates through high values of the rotational quantum number J. Other transitions assigned are c-type R-branch and P-branch transitions between these two substates and a-type lines within the e1 and o1 substates. The assignments were facilitated by initial analysis of the strong Q-branch series, as recorded by the fast scan submillimeter spectroscopy technique (FASSST). The assigned lines of CH2DOH include the first inter-state transitions in the sub-millimeter-wave region and the first to possess high J-values. The completeness of the data generated by FASSST and the success of a simple power series analysis suggest that many parts of the spectrum of CH2DOH may be far more tractable than previously believed. The data should be useful in the development of a full Hamiltonian and in the assignment of astronomical emission f...

The degree of overheating of a melt often plays an important role in the response of the melt to subsequent undercooling, it determines the nucleation and growth behavior and the properties of the final crystalline products. However, the dependence of accessible undercooling of different bulk melt samples on prior liquid overheating has been reported to exhibit a variety of specific features which could not be given a satisfactory explanation so far. In order to determine uniquely the dependence of accessible undercooling on prior overheating and the possible factors affecting it, the solidification of a pure Sn single micro-sized droplet was studied by differential fast scanning calorimeter with cooling rates in the range from 500 to 10 000 K/s. It is observed experimentally that (i) the degree of undercooling increases first gradually with increase of prior overheating; (ii) if the degree of prior superheating exceeds a certain limiting value, then the accessible undercooling increases always with increasing cooling rate; in the alternative case of moderate initial overheating, the degree of undercooling reaches an undercooling plateau; and (iii) in latter case, the accessible undercooling increases initially with increasing cooling rate. However, at a certain limiting value of the cooling rate this kind of response is qualitatively changed and the accessible undercooling decreases strongly with a further increase of cooling rate. The observed rate dependent behavior is consistent with a kinetic model involving cavity induced heterogeneous nucleation and cavity size dependent growth. This mechanism is believed to be relevant also for other similar rapid solidification nucleation processes.

The experimentally accessible degree of undercooling of single micron-sized liquid pure tin drops has been studied via differential fast scanning calorimetry. The cooling rates employed ranged from 100 to 14 000 K/s. The diameter of the investigated tin drops varied in the range from 7 to 40 μm. The influence of the drop shape on the solidification process could be eliminated due to the nearly spherical shape of the single drop upon heating and cooling and the resultant geometric stability. As a result it became possible to study the effect of both drop size and cooling rate in rapid solidification experimentally. A theoretical description of the experimental results is given by assuming the existence of two different heterogeneous nucleation mechanisms leading to crystal nucleation of the single tin drop. In agreement with the experiment these mechanisms yield a shelf-like dependence of crystal nucleation on undercooling. A dependence of crystal nucleation on the size of the tin drop was observed and is discussed in terms of the mentioned theoretical model, which can possibly also describe the nucleation for other related rapid solidification processes.

We evaluate the efficiency of multiple variants of energy landscape paving in all-atom simulations of the trp-cage protein using a recently developed new force field. Especially, we introduce a temperature-free variant of the method and demonstrate that it allows a fast scanning of the energy landscape. Nativelike structures are found in less time than by other techniques. The sampled low-energy configurations indicate a funnel-like energy landscape.