3,006 research outputs found
Prediction of Novel High Pressure H2O-NaCl and Carbon Oxide Compounds with Symmetry-Driven Structure Search Algorithm
Crystal structure prediction with theoretical methods is particularly
challenging when unit cells with many atoms need to be considered. Here we
employ a symmetry-driven structure search (SYDSS) method and combine it with
density functional theory (DFT) to predict novel crystal structures at high
pressure. We sample randomly from all 1,506 Wyckoff positions of the 230 space
groups to generate a set of initial structures. During the subsequent
structural relaxation with DFT, existing symmetries are preserved, but the
symmetries and the space group may change as atoms move to more symmetric
positions. By construction, our algorithm generates symmetric structures with
high probability without excluding any configurations. This improves the search
efficiency, especially for large cells with 20 atoms or more. We apply our
SYDSS algorithm to identify stoichiometric (H2O)_n-(NaCl)_m and C_nO_m
compounds at high pressure. We predict a novel H2O-NaCl structure with Pnma
symmetry to form at 3.4 Mbar, which is within the range of diamond anvil
experiments. In addition, we predict a novel C2O structure at 19.8 Mbar and C4O
structure at 44.0 Mbar with Pbca and C2/m symmetry respectively.Comment: 8 pages,8 figures, 3 table, Physical Review B, 201
Laplacian Distribution and Domination
Let denote the number of Laplacian eigenvalues of a graph in an
interval , and let denote its domination number. We extend the
recent result , and show that isolate-free graphs also
satisfy . In pursuit of better understanding Laplacian
eigenvalue distribution, we find applications for these inequalities. We relate
these spectral parameters with the approximability of , showing that
. However, for -cyclic graphs, . For trees ,
A Luddite Archaeology of Hobbyist Computation
The practice element of this research includes the How-To documented here, as well as the collected recordings and artist events I have documented. It also includes the forms I have chosen and experimented with for the publication of this. This text was written primarily as a website, and the styling of different sections here references the web version. To read the website version visit: http://bruise.in/research/luddite-archaeology.html. Some additional notes on the construction of the page are included in the code which can be viewed in the inspector. Excerpts of the code are included in the Code Practice section
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