Structural principles of semiconducting Group 14 clathrate frameworks

Area of Science:

• Materials Science
• Solid-State Chemistry
• Computational Chemistry

Background:

• Clathrate frameworks are cage-like structures with potential applications in thermoelectric materials.
• Group 14 elements (carbon, silicon, germanium, tin) form diverse clathrate structures.
• Understanding structure-property relationships is crucial for designing new materials.

Purpose of the Study:

• To theoretically investigate the structural principles and electronic properties of Group 14 clathrate frameworks.
• To explore basic clathrates, polytypes, intergrowth, and extended frameworks.
• To identify promising compositions for experimental realization.

Main Methods:

• Comprehensive theoretical investigation using quantum chemical calculations.
• Employed the PBE0 hybrid density functional method.
• Analyzed structural trends, electronic properties, band structures, and simulated X-ray patterns.

Main Results:

• Clathrate II framework is energetically most favorable, with novel hexagonal polytypes also highly favorable.
• Several silicon-based clathrate frameworks exhibit direct and wide band gaps.
• Provided band structure diagrams and simulated powder X-ray patterns for various frameworks.

Conclusions:

• Novel hexagonal polytypes of clathrate II are energetically competitive and promising for electronic applications.
• Silicon clathrates with wide, direct band gaps are identified, suggesting potential for semiconductor applications.
• Preliminary evaluation of guest-occupied frameworks offers insights into experimentally feasible clathrate compositions.