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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on SiB3 by Materials Project

SiB3 crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. there are four inequivalent B sites. In the first B site, B is bonded in a 6-coordinate geometry to five B and one Si atom. There are a spread of B–B bond distances ranging from 1.75–1.80 Å. The B–Si bond length is 1.98 Å. In the second B site, B is bonded in a 1-coordinate geometry to five B and one Si atom. There are a spread of B–B bond distances ranging from 1.77–1.85 Å. The B–Si bond length is 2.04 Å. In the third B site, B is bonded in a 6-coordinate geometry to six B atoms. There are a spread of B–B bond distances ranging from 1.72–1.93 Å. In the fourth B site, B is bonded in a 6-coordinate geometry to five B and one Si atom. The B–Si bond length is 2.01 Å. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 2-coordinate geometry to two equivalent B and three Si atoms. There are one shorter (2.34 Å) and two longer (2.59 Å) Si–Si bond lengths. In the second Si site, Si is bonded in a distorted bent 120 degrees geometry to two B and two equivalent Si atoms.

36 MATERIALS SCIENCE↗
NASA NTRS2021

Modeling Snow Ablation over the Western United States Mountains: Patterns and Controlling Factors

When compared with differences in snow accumulation predicted by widely used hydrological models, there is a much greater divergence among otherwise “good” models in their simulation of the snow ablation process. Here, we explore differences in the performance of the Variable Infiltration Capacity model (VIC), Noah land surface model with multiparameterization options (Noah-MP), the Catchment model, and the third-generation Simplified Simple Biosphere model (SiB3) in their ability to reproduce observed snow water equivalent (SWE) during the ablation season at 10 Snowpack Telemetry (SNOTEL) stations over 1992–2012. During the ablation period, net radiation generally has stronger correlations with observed melt rates than does air temperature. Average ablation rates tend to be higher (in both model predictions and observations) at stations with a large accumulation of SWE. The differences in the dates of last snow between models and observations range from several days to approximately a month (on average 5.1 days earlier than in observations). If the surface cover in the models is changed from observed vegetation to bare soil in all of the models, only the melt rate of the VIC model increases. The differences in responses of models to canopy removal are directly related to snowpack energy inputs, which are further affected by different algorithms for surface albedo and energy allocation across the models. We also find that the melt rates become higher in VIC and lower in Noah-MP if the shrub/grass present at the observation sites is switched to trees.

Snow↗