How do quantum effects change conclusions about heterogeneous cluster behavior based on classical mechanics simulations?

Abstract

Comparisons of classical and quantum Monte Carlo simulation of SF 6-͑Ar͒ n and SF 6-͑Ne͒ n clusters are used to examine whether certain novel types of behavior seen in classical simulations of SF 6-͑Ar͒ n and SF 6-͑Kr͒ n persist when quantum effects are taken into account. For mixed clusters formed from Ar ͑and presumably other heavy partners͒ quantum effects have little effect on calculated properties, even at very low temperatures, so the cluster-size-dependent preference for solvation vs phase separation and ''reverse melting'' behavior found in the classical simulations may be expected to occur in many heterogeneous systems. On the other hand, quantum effects substantially lower the melting temperatures of clusters formed with Ne, and ͑except for a couple of unusually stable stacked isomers͒ effectively remove the barriers separating the maximally-solvated and phase-separated forms, implying that the latter will normally not exist. Moreover, for ͑at least͒ the SF 6-͑Ne͒ 11 species, when quantum effects are taken into account there is little evidence of solidlike behavior down to the lowest temperatures accessible to our simulation ͑0.4 K͒, although classical simulations show a sharp freezing transition at 1.5(Ϯ0.1) K. Inclusion of three-body triple-dipole Axilrod-Teller-Muto interactions in the overall potential energy has little effect on either quantum or classical Ne cluster simulations.

Anomalous Fluorescence of Terrylene in Neon Matrix

“…Increased mobility of the matrix does not seem to be sufficient and does not lead to anomalous fluorescence of terrylene. Possibly, the quantum mechanical effects , operating in the Ne matrix should be included to explain our observation. We are however not ready to discuss this point at the present state of our knowledge.…”

Quantum partition functions from classical distributions: Application to rare-gas clusters

“…Quantum systems can also be studied by numerical simulation, and the most rigorous approaches at finite temperature are based on the path-integral treatment of quantum mechanics. Path-integral Monte Carlo ͑PIMC͒ methods have proven extremely useful and successful in predicting the thermodynamics properties of many condensed matter systems, 2,3 and, more recently, of finite atomic [4][5][6][7] and molecular 8 clusters. Two kinds of PIMC methods are in use, namely the Fourier-path-integral ͑FPI͒ ͑Ref.…”