Blue moon sampling

Ciccotti, G. Kapral, R. Vanden-Eijnden, E., Blue moon sampling, vectorial reaction coordinates, and unbiased constrained dynamics, Chem. Phys. Chem. 2005, 6, 1809-1814... 

To generalize the zero- or the finite-temperature string methods to work in collective variables (Sects. 6.4 and 6.5), it suffices to do the following. At each iteration, it is now required to estimate the tensor A fiO) defined in (94) and determine the gradient of the density M 9) defined in (93) to be used in the equivalent of (125) (in the zero-temperature version) or sample with respect to this density to identify the equivalent of (127) (in the finite-temperature version). This requires to introduce an additional loop of sampling of blue moon type, now in the original ensemble with density m(x) under the additional constraint that 0 x) = 6. For details, see [23]. 

We have studied the intracage oxidation NO2 + O2 —t NO3 in sodalite by means of the Blue Moon Ensemble and Car Parrinello Molecular Dynamics combined methods. The reaction was simulated by following the inverse reduction process. Such an approach has allowed an easier application of the BME sampling and could be of general interest. 

The Fe2+ —> Ti4 IVCT transition has been identified in the spectra of other titanian pyroxenes, including samples from the Moon (Bums et al., 1976 Dowty, 1978) and, perhaps, a blue titaniferous omphacite from Labrador (Curtis et al., 1975). An intense broad band in this omphacite centred around 15,000 cm-1 and showing a pressure-induced shift to lower energies was originally assigned to Fe2+ -> Fe3+ IVCT (Abu-Eid, 1976) but later it was reassigned as a Fe2+ - Ti4+ IVCT transition (Strens et al., 1982). 

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