Cation disorder and thermoelectric properties in layered ternary compounds MBi2Te4 (M=Ge, Sn)

Statistical learning algorithms are finding more and more applications in science and technology. Atomic-scale modeling is no exception, with machine learning becoming commonplace as a tool to predict energy, forces and properties of molecules and condensed-phase systems. This short review summarizes recent progress in the field, focusing in particular on the problem of representing an atomic configuration in a mathematically robust and computationally efficient way. We also discuss some of the regression algorithms that have been used to construct surrogate models of atomic-scale properties. We then show examples of how the optimization of the machine-learning models can both incorporate and reveal insights onto the physical phenomena that underlie structure–property relations.

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High-pressure crystallography

Acta Crystallographica Section A Foundations of Crystallography ◽

10.1107/s0108767307061181 ◽

2007 ◽

Vol 64 (1) ◽

pp. 135-148 ◽

Cited By ~ 118

Author(s):

Andrzej Katrusiak

Keyword(s):

Crystal Structure ◽

High Pressure ◽

Solid State And Materials ◽

Atomic Scale ◽

Structural Studies ◽

Structure Property ◽

Property Relations ◽

Pressure Calibration ◽

Radiation Sources ◽

High Pressure Crystallography

Since the late 1950's, high-pressure structural studies have become increasingly frequent, following the inception of opposed-anvil cells, development of efficient diffractometric equipment (brighter radiation sources both in laboratories and in synchrotron facilities, highly efficient area detectors) and procedures (for crystal mounting, centring, pressure calibration, collecting and correcting data). Consequently, during the last decades, high-pressure crystallography has evolved into a powerful technique which can be routinely applied in laboratories and dedicated synchrotron and neutron facilities. The variation of pressure adds a new thermodynamic dimension to crystal-structure analyses, and extends the understanding of the solid state and materials in general. New areas of thermodynamic exploration of phase diagrams, polymorphism, transformations between different phases and cohesion forces, structure–property relations, and a deeper understanding of matter at the atomic scale in general are accessible with the high-pressure techniques in hand. A brief history, guidelines and requirements for performing high-pressure structural studies are outlined.

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Probing vacancies and structural distortions at individual defects in ceramics using EELS

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100165859 ◽

1996 ◽

Vol 54 ◽

pp. 678-679

Author(s):

D. J. Wallis ◽

N. D. Browning

Keyword(s):

Structural Information ◽

Core Loss ◽

Nearest Neighbors ◽

Ceramic Materials ◽

Scanning Transmission Electron Microscope ◽

Real Space ◽

Atomic Scale ◽

Structure Property ◽

Scanning Transmission ◽

Key Issues

In electron energy loss spectroscopy (EELS), the near-edge region of a core-loss edge contains information on high-order atomic correlations. These correlations give details of the 3-D atomic structure which can be elucidated using multiple-scattering (MS) theory. MS calculations use real space clusters making them ideal for use in low-symmetry systems such as defects and interfaces. When coupled with the atomic spatial resolution capabilities of the scanning transmission electron microscope (STEM), there therefore exists the ability to obtain 3-D structural information from individual atomic scale structures. For ceramic materials where the structure-property relationships are dominated by defects and interfaces, this methodology can provide unique information on key issues such as like-ion repulsion and the presence of vacancies, impurities and structural distortion.An example of the use of MS-theory is shown in fig 1, where an experimental oxygen K-edge from SrTiO3 is compared to full MS-calculations for successive shells (a shell consists of neighboring atoms, so that 1 shell includes only nearest neighbors, 2 shells includes first and second-nearest neighbors, and so on).

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Structure-Property Relations Two-Dimensional Halide Perovskites

10.29363/nanoge.ngfm.2019.156 ◽

2019 ◽

Author(s):

Constantinos Stoumpos

Keyword(s):

Two Dimensional ◽

Structure Property ◽

Property Relations ◽

Halide Perovskites

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Jaws of Platynereis dumerilii: Miniature Biogenic Structures with Hardness Properties Similar to Those of Crystalline Metals

JOM ◽

10.1007/s11837-021-04702-1 ◽

2021 ◽

Author(s):

Luis Zelaya-Lainez ◽

Giuseppe Balduzzi ◽

Olaf Lahayne ◽

Kyojiro N. Ikeda ◽

Florian Raible ◽

...

Keyword(s):

Inductively Coupled Plasma ◽

Indentation Depth ◽

Organic Matrix ◽

Structure Property ◽

Structural Protein ◽

Inductively Coupled ◽

Property Relations ◽

Biogenic Structures ◽

Platynereis Dumerilii ◽

Bristle Worms

AbstractNanoindentation, laser ablation inductively coupled plasma mass spectroscopy and weighing ion-spiked organic matrix standards revealed structure-property relations in the microscopic jaw structures of a cosmopolitan bristle worm, Platynereis dumerilii. Hardness and elasticity values in the jaws’ tip region, exceeding those in the center region, can be traced back to more metal and halogen ions built into the structural protein matrix. Still, structure size appears as an even more relevant factor governing the hardness values measured on bristle worm jaws across the genera Platynereis, Glycera and Nereis. The square of the hardness scales with the inverse of the indentation depth, indicating a Nix-Gao size effect as known for crystalline metals. The limit hardness for the indentation depth going to infinity, amounting to 0.53 GPa, appears to be an invariant material property of the ion-spiked structural proteins likely used by all types of bristle worms. Such a metal-like biogenic material is a major source of bio-inspiration.

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Polymer Dynamics in Nanostructured Environments: Structure-Property Relations Unraveled by Dielectric Spectroscopy

ACS Symposium Series - Broadband Dielectric Spectroscopy: A Modern Analytical Technique ◽

10.1021/bk-2021-1375.ch010 ◽

2021 ◽

pp. 223-238

Author(s):

Martin Tress ◽

Maximillian Vielhauer ◽

Pierre Lutz ◽

Rolf Mülhaupt ◽

Friedrich Kremer ◽

...

Keyword(s):

Dielectric Spectroscopy ◽

Polymer Dynamics ◽

Structure Property ◽

Property Relations

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Ab initio molecular dynamics and materials design for embedded phase-change memory

npj Computational Materials ◽

10.1038/s41524-021-00496-7 ◽

2021 ◽

Vol 7 (1) ◽

Cited By ~ 1

Author(s):

Liang Sun ◽

Yu-Xing Zhou ◽

Xu-Dong Wang ◽

Yu-Han Chen ◽

Volker L. Deringer ◽

...

Keyword(s):

Phase Change ◽

High Performance ◽

Materials Design ◽

Atomic Scale ◽

Ab Initio Molecular Dynamics ◽

Core Material ◽

Structure Property ◽

Switching Speed ◽

Atomic Structures ◽

Memory Applications

AbstractThe Ge2Sb2Te5 alloy has served as the core material in phase-change memories with high switching speed and persistent storage capability at room temperature. However widely used, this composition is not suitable for embedded memories—for example, for automotive applications, which require very high working temperatures above 300 °C. Ge–Sb–Te alloys with higher Ge content, most prominently Ge2Sb1Te2 (‘212’), have been studied as suitable alternatives, but their atomic structures and structure–property relationships have remained widely unexplored. Here, we report comprehensive first-principles simulations that give insight into those emerging materials, located on the compositional tie-line between Ge2Sb1Te2 and elemental Ge, allowing for a direct comparison with the established Ge2Sb2Te5 material. Electronic-structure computations and smooth overlap of atomic positions (SOAP) similarity analyses explain the role of excess Ge content in the amorphous phases. Together with energetic analyses, a compositional threshold is identified for the viability of a homogeneous amorphous phase (‘zero bit’), which is required for memory applications. Based on the acquired knowledge at the atomic scale, we provide a materials design strategy for high-performance embedded phase-change memories with balanced speed and stability, as well as potentially good cycling capability.

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Atomic Scale Structure-Property Relationships of Defects and Interfaces in Ceramics

Microscopy and Microanalysis ◽

10.1017/s143192760002290x ◽

1998 ◽

Vol 4 (S2) ◽

pp. 556-557

Author(s):

S. Stemmer ◽

G. Duscher ◽

E. M. James ◽

M. Ceh ◽

N.D. Browning

Keyword(s):

Point Defects ◽

High Resolution Electron Microscopy ◽

Complete Characterization ◽

Atomic Scale ◽

Structure Property ◽

Defect Engineering ◽

Impurity Atoms ◽

Structure Property Relationships ◽

Resolution Electron ◽

Scale Composition

The evaluation of the two dimensional projected atom column positions around a defect or an interface in an electronic ceramic, as it has been performed in numerous examples by (quantitative) conventional high-resolution electron microscopy (HRTEM), is often not sufficient to relate the electronic properties of the material to the structure of the defect. Information about point defects (vacancies, impurity atoms), and chemistry or bonding changes associated with the defect or interface is also required. Such complete characterization is a necessity for atomic scale interfacial or defect engineering to be attained.One instructive example where more than an image is required to understand the structure property relationships, is that of grain boundaries in Fe-doped SrTi03. Here, the different formation energies of point defects cause a charged barrier at the boundary, and a compensating space charge region around it. The sign and magnitude of the barrier depend very sensitively on the atomic scale composition and chemistry of the boundary plane.

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