Novel Graphene Allotropes Designed by Polymerizing Pyracyclene Molecules

Our detailed first-principles calculations suggest the assembly of dehydrogenated pyracyclene molecules to give novel graphene allotropes with high stabilities. The allotrope with C4 square conjunction connecting neighboring pyracyclene-based motifs is a Dirac semimetal with tunable velocities of the massless Fermion carriers, which could be increased by ∼7 × 105 m/s by tensile strain. Another allotrope with a C6 hexagon as the conjunction unit is semiconducting, which could be a good photovoltaic material due to its 1.20 eV band gap to meet the sunlight absorption and the high charge carrier mobilities of ∼104 cm2 V–1 S–1 to help suppress recombination of the light-induced electrons and holes. Furthermore, the continuous tuning of its band gap in a wide range by strain and the sponge-like ultrasoft mechanical properties to facilitate strain loading on experiment make it attractive for next-generation nanoelectronics. In addition, the stacked allotrope layers could also find use for lithium-ion battery anodes because of their high Li capacities of 638 and 1117 mAh/g, good charging and discharging kinetics of Li, and moderate average open-circuit voltages, respectively

Composite means of climate indices for different SLP anomaly regimes.

<p>Composite means of climate indices for different SLP anomaly regimes.</p

Time series of the number of DJF months belonging to each regime (a-e) and the normalized DJF-mean PV-based EAWM index (f).

<p>The EAWM index is normalized to have a mean of zero and a standard deviation of one during 1948–2014.</p

The average Sample Area-Weighted-PC for all samples for the <i>M</i> clusters under different values of <i>M</i> (2–6) based on the distance-based <i>k</i>-means, Area-Weighted-PC-based <i>k</i>-means, and SOM clustering methods.

<p>Note that result for the Area-Weighted-PC-based <i>k</i>-means method is estimated as the column-average of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158122#pone.0158122.t001" target="_blank">Table 1</a>. In the SOM, when the number of clusters is set to 4 or 6, there are two possible configurations of the SOM grids, i.e., 1×4 and 2×2 for <i>M</i> = 4, and 1×6 and 2×3 for <i>M</i> = 6. Data are presented with 2 digits.</p

The minimum of the averages of Sample Area-Weighted-PC for the <i>M</i> clusters under different values of the critical threshold for Area-Weighted-PC (0.3–0.8) and <i>M</i> (2–6).

<p>Due to the same reason given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158122#pone.0158122.t001" target="_blank">Table 1</a>, data are presented with 6 digits.</p

Same as Table 4, except for the minimum of the averages of Sample Area-Weighted-PC for the <i>M</i> clusters.

<p>Note that result for the Area-Weighted-PC-based <i>k</i>-means method is estimated as the column-average of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158122#pone.0158122.t002" target="_blank">Table 2</a>.</p

DJF climatology of SLP and surface winds and composite mean monthly anomalies of SLP and surface winds over the Northern Hemisphere associated with each cluster.

<p>a. DJF-mean SLP (shading; hPa) and surface winds (vector; m s^–1) at 10-m height above surface. The area within the blue lines indicates the region (20–160°E, 10–90°N) under consideration by the clustering method. b-f. Composite mean monthly anomalies of SLP and surface winds for each cluster. Statistical significance is evaluated using the 95% confidence level based on the Student’s <i>t</i> test. Composited SLP anomalies are plotted if they are significant. Wind anomalies are plotted if wind anomalies are significant in at least one direction (east–west or north–south). The ratio of the number of samples belonging to each regime to the total number of samples is included at the top left of each panel. The average spatial pattern correlation coefficient for each regime is shown separately at the top right corner of each panel. All quantities are based on the NCEP-NCAR reanalysis from December 1948 through February 2015.</p

A Novel Two-Dimensional Allotrope of Silicon Grown on Al(111): A Case Study of the Interface Effect

Based on density functional calculations, a novel planar allotrope of silicon on Al(111) is rationally designed by using the lowest energy principle, which is also predicted to be stable above room temperature to suggest the possibility for its fabrication. The corresponding free-standing sheet would be buckled though the structural characteristics still remain, whose stability has also been evaluated in detail. It has been found to have strong anisotropic properties to be as hard as silicene in a specific direction and to be very soft in the perpendicular direction. Surprisingly, a peculiar negative Poisson’s ratio showing unusual mechanical properties is also found. The indirect bandgap of 0.14 eV of the free-standing sheet could be closed by applying tensile strain. Interestingly, the Dirac cone of the orthogonal lattice allotrope sheet can be obtained by applying biaxial strain, for which the velocity of the charge carriers could reach 5.97 × 105 m/s. In addition, the hydrogenated sheet is also quite stable and may find usage for sunlight absorption, field-effect transistor, etc., which may be decorated with Ti, Fe, or Co adsorptions to have half-metallic conducting properties for spin filtering

The average Sample Area-Weighted-PC for all samples for applications of the clustering algorithm to DJF SLP anomalies using different values of the critical threshold for Area-Weighted-PC (0.3–0.8) and <i>M</i> (2–6).

<p>To keep consistence with the criterion (10⁻⁶) for iteration during clustering, results are presented with 6 digits.</p

An approach to localization for ensemble-based data assimilation - Fig 5

<p>Comparisons between 2D filter presented by the GC correlation function (d) and the expansion with different truncations: <i>K</i> = 10 (a); <i>K</i> = 15 (b); and <i>K</i> = 20 (c).</p