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The Synthesis of [Sn10(Si(SiMe3)3)4]2- Using a Metastable Sn(I) Halide Solution Synthesized via a Co-condensation Technique
Published on: November 28, 2016
Novel hexagonal polytypes of silver: growth, characterization and first-principles calculations
Indrani Chakraborty1, Daniel Carvalho, Sharmila N Shirodkar
1Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai 400005, India.
Summary
Researchers explored how dimensional and kinetic factors influence metastable silver polytypes. Slowing growth kinetics enabled production of the 4H polytype in thin films and a novel 2H polytype, offering new avenues in materials science.
Area of Science:
- Materials Science
- Solid-State Physics
- Crystallography
Background:
- Metastable polytypes of metallic silver are typically observed only in size-constrained systems.
- Understanding the factors controlling their formation is crucial for materials design.
Purpose of the Study:
- To investigate the relative effects of dimensional and kinetic constraints on stabilizing metastable silver polytypes.
- To explore the synthesis and properties of novel silver polytypes.
Main Methods:
- Controlled kinetic growth of silver thin films.
- First-principles calculations using density functional theory.
- Phonon dispersion analysis for stability assessment.
Main Results:
- The hexagonal 4H silver polytype was produced in bulk thin films by slowing growth kinetics.
- A novel two-dimensional, metastable 2H silver polytype was synthesized under extremely slow growth conditions.
- The 2H polytype exhibits high reactivity, a 23% lower density, and marginal stability due to a flat energy surface and high configurational entropy.
Conclusions:
- Kinetic control, specifically slowing growth rates, is a viable strategy for producing metastable silver polytypes.
- The novel 2H silver polytype's metastability is linked to its unique structural and energetic properties.
- This study expands the understanding of polytypism in metallic systems and offers pathways for novel material synthesis.
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