5 research outputs found
Charge Localization and Ordering in AMnO Hollandite Group Oxides: Impact of Density Functional Theory Approaches
The phases of AMnO hollandite group oxides emerge from the
competition between ionic interactions, Jahn-Teller effects, charge ordering,
and magnetic interactions. Their balanced treatment with feasible computational
approaches can be challenging for commonly used approximations in Density
Functional Theory. Three examples (A = Ag, Li and K) are studied with a
sequence of different approximate exchange-correlation functionals. Starting
from a generalized gradient approximation (GGA), an extension to include van
der Waals interactions and a recently proposed meta-GGA are considered. Then
local Coulomb interactions for the Mn electrons are more explicitly
considered with the DFT+ approach. Finally selected results from a hybrid
functional approach provide a reference. Results for the binding energy of the
A species in the parent oxide highlight the role of van der Waals interactions.
Relatively accurate results for insertion energies can be achieved with a low
and a high approach. In the low case, the materials are described
as band metals with a high symmetry, tetragonal crystal structure. In the high
case, the electrons donated by A result in formation of local Mn
centers and corresponding Jahn-Teller distortions characterized by a local
order parameter. The resulting degree of monoclinic distortion depends on
charge ordering and magnetic interactions in the phase formed. The reference
hybrid functional results show charge localization and ordering. Comparison to
low temperature experiments of related compounds suggests that charge
localization is the physically correct result for the hollandite group oxides
studied here. . . .Comment: 16 pages, 8 figure
Seagrass photosynthesis per area and day.
<p>Measures are mean ±SE, and lower-case letters above bars indicate treatments separated by Student–Newman–Keuls post hoc analyses (<i>p</i> < 0.05). For abbreviations, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0181386#pone.0181386.g001" target="_blank">Fig 1</a>.</p
Results of one-way ANOVA testing differences between control and all treatments in maximum electron transport rate (ETR<sub>max</sub>, μmol e<sup>−</sup>m<sup>–2</sup> s–1), initial slope of the RLC (α) and saturation irradiance (<i>E</i><sub>k,</sub> μmol<sub>photons</sub> m<sup>–2</sup> s<sup>–1</sup>)<sub>,</sub> productivity (P, gCO<sub>2</sub> gDW<sup>–1</sup>), and P/R ratios for the whole plant (P/R<sub>plant</sub>), photosynthetic tissue (P/R<sub>ps</sub>), and non-photosynthetic tissue (P/R<sub>nps</sub>).
<p>Post hoc analyses are performed using the Student–Newman–Keuls method. Significant values (<i>p</i> < 0.05) are shown in bold.</p
Calculated diel net productivity as CO<sub>2</sub> fixation per meadow area and day, shown as a range of minimum and maximum values (for the calculations, see “Materials and methods”).
<p>In the boxes, lines in middle indicate means, upper and lower lines indicate the 75 and 25 quartiles, respectively, upper and lower whiskers indicate maximum and minimum values, respectively, and circles indicate outliers. Lower-case letters above bars indicate treatments separated by Student–Newman–Keuls post hoc analyses (<i>p</i> < 0.05). For abbreviations, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0181386#pone.0181386.g001" target="_blank">Fig 1</a>.</p
Results of two-way ANOVAs testing the effects of shoot age and treatment on internode length and internode number.
<p>Significant values (<i>p</i> < 0.05) are shown in bold.</p