2 research outputs found
Anion-polarisation--directed short-range-order in antiperovskite LiFeSO
Short-range ordering in cation-disordered cathodes can have a significant
effect on their electrochemical properties. Here, we characterise the cation
short-range order in the antiperovskite cathode material LiFeSO, using
density functional theory, Monte Carlo simulations, and synchrotron X-ray
pair-distribution-function data. We predict partial short-range
cation-ordering, characterised by favourable OLiFe oxygen coordination
with a preference for polar cis-OLiFe over non-polar
trans-OLiFe configurations. This preference for polar cation
configurations produces long-range disorder, in agreement with experimental
data. The predicted short-range-order preference contrasts with that for a
simple point-charge model, which instead predicts preferential
trans-OLiFe oxygen coordination and corresponding long-range
crystallographic order. The absence of long-range order in LiFeSO can
therefore be attributed to the relative stability of cis-OLiFe and
other non-OLiFe oxygen-coordination motifs. We show that this effect is
associated with the polarisation of oxide and sulfide anions in polar
coordination environments, which stabilises these polar short-range cation
orderings. We propose similar anion-polarisation-directed short-range-ordering
may be present in other heterocationic materials that contain cations with
different formal charges. Our analysis also illustrates the limitations of
using simple point-charge models to predict the structure of cation-disordered
materials, where other factors, such as anion polarisation, may play a critical
role in directing both short- and long-range structural correlations
Quantifying Tectonic and Glacial Controls on Topography in the Patagonian Andes (46.5°S) From Integrated Thermochronometry and Thermo‐Kinematic Modeling
The Patagonian Andes have been used to illustrate the dependency of major topographic changes in response to glacial erosion processes dominating over tectonic deformation and uplift. Here, we investigate tectonic and glacial contributors to the erosion history and evolution of topography in the Patagonian Andes at 46.5°S. We present 33 new apatite and zircon (U‐Th)/He (AHe and ZHe, respectively) and fission track (AFT and ZFT, respectively) ages integrated with 46 previously published bedrock thermochronometric ages in a 3D thermo‐kinematic model. Observed thermochronometer ages increase from the eastern flank of the topographic crest of the orogen toward the eastern retro‐foreland basin (from AFT 4–10 Ma, ZHe 4–12 Ma, ZFT 6–14 Ma to AFT 28–32 Ma, ZHe 68–117 Ma). Thermo‐kinematic modeling indicates that spatial gradients in thermochronometric ages can be explained by an up to 100‐km‐wide, parabolic‐shaped pattern in exhumation rates with a maximum rate of 0.5 mm/yr from 15 Ma until the onset of glaciation at ∼7 Ma. Furthermore, model results suggest that the youngest AHe ages require a localized acceleration in erosion from ∼0.5 mm/yr to ∼2.2 mm/yr starting between ∼5 and ∼3 Ma, coeval with intensified glaciation and subduction of the Chile Rise. Our results suggest that the long‐wavelength (∼100 km) topography and erosion patterns are likely controlled by rock uplift above mid‐crustal ramp(s) and subsequent transpression along the Liquiñe‐Ofqui Fault. Superposed on these tectonic processes, Late Cenozoic glaciation resulted in localized and accelerated erosion over wavelengths of <20 km.Key Points:
Low‐temperature thermochronology records non‐uniform erosion in the retro‐wedge of the Southern Patagonian Andes.
Erosion pattern and long‐wavelength topography are largely a function of regional tectonic activity over the last 15 Myr.
Glaciation has modified erosion rates and topography on sub‐valley scales over the last 5–3 Myr.Deutsche Forschungsgemeinschaft (DFG)
http://dx.doi.org/10.13039/501100001659MINEDUC | CONICYT | Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)
http://dx.doi.org/10.13039/50110000285