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Full-Text Articles in Physical Sciences and Mathematics
Structure Analysis Of Natural Wangdaodeite—Linbo3-Type Fetio3, Oliver Tschauner, Chi Ma, Matthew G. Newville, Antonio Lanzirotti
Structure Analysis Of Natural Wangdaodeite—Linbo3-Type Fetio3, Oliver Tschauner, Chi Ma, Matthew G. Newville, Antonio Lanzirotti
Geoscience Faculty Research
© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This paper reports the first structure refinement of natural wangdaodeite, LiNbO3-type FeTiO3 from the Ries impact structure. Wangdaodeite occurs together with recrystallized ilmenite clasts in shock melt veins which have experienced peak shock pressures of between 17 and 22 GPa. Comparison of natural and synthetic wangdaodeite points toward a correlation between the distortion of ferrate-and titanate-polyhedra and the c/a ratio of the unit cell. The Raman spectrum of wangdaodeite is calculated based on the refined structure. Comparison to the reported spectrum of the type-material shows that the Raman peak at 738–740 …
Structure-Strength Relations Of Distinct Mon Phases From First-Principles Calculations, Cheng Lu, Changfeng Chen
Structure-Strength Relations Of Distinct Mon Phases From First-Principles Calculations, Cheng Lu, Changfeng Chen
Physics & Astronomy Faculty Research
Molybdenum mononitrides (MoN) exhibit superior strength and hardness among the large class of transition-metal light-element compounds, but the underlying atomistic mechanisms for their outstanding mechanical properties and the variations of those properties among various MoN phases adopting different crystal structures remain largely unexplored and require further investigation. Here we report first-principles calculations that examine the stress-strain relations of these materials, and systematically compare results under pure and indentation shear deformations. In particular, we examine the distinct bonding structures and the associated mechanical properties in four different crystal phases of MoN that have been experimentally synthesized and stabilized under various physical …
Indentation-Strain Stiffening In Tungsten Nitrides: Mechanisms And Implications, Cheng Lu, Changfeng Chen
Indentation-Strain Stiffening In Tungsten Nitrides: Mechanisms And Implications, Cheng Lu, Changfeng Chen
Physics & Astronomy Faculty Research
We report on a systematic computational study of ideal strengths, i.e., the lowest stresses needed to destabilize a perfect crystal under a variety of loading conditions for six stable and metastable tungsten nitrides identified by advanced crystal structure search algorithms. We employ first-principles calculations to determine stress-strain relations and examine the corresponding atomistic bonding changes for a microscopic understanding of the structural deformation modes. The obtained results show that, in stark contrast to many previously studied transition-metal borides, carbides, and also most nitrides, the tungsten nitrides exhibit surprisingly broad and common patterns of strain-stiffening effects under indentation strains. These extraordinary …