Metavalent Bonding

May 4, 2023

Metavalent bonding is a newly discovered chemical bonding phenomenon that has caught the attention of the scientific community. This bonding mechanism is found in solids and exhibits a unique property that can conduct electricity like a metal and heat like a glass. This property is known to tailor the thermoelectric performance of quantum materials and convert waste heat to electricity.

zT and the material constants that constitute it

The performance evaluation of a material is done by using the thermoelectric index known as zT, which is a dimensionless index that considers the electrical resistivity, Seebeck coefficient, and thermal conductivity. Efficiency is directly proportional to zT, meaning that the higher the zT value, the better the efficiency. Nevertheless, increasing the zT value is a daunting task due to the interdependencies between the material constants that constitute zT, which are in contradiction with each other.

New Research Breakthrough

Researchers have recently turned to chemical bonding in solids to optimize thermoelectric performance in quantum materials. They utilized metavalent bonding, a chemical bond possessing qualities of both metallic and glass bonding, to achieve low thermal conductivity in materials.

TlBiSe2 and its behavior

The researchers analyzed TlBiSe2, a renowned topological insulator, by synchrotron X-ray pair distribution function experiment done in Petra-III, DESY, Germany. Due to the influence of metavalent bonding, the material displayed a lattice shearing phenomenon resulting from local distortion caused by dual lone pair induction. Atoms in a locally distorted crystal exhibit slightly distorted positions.

The highest reported zT among n-type thallium chalcogenides for TlBiSe2 is around 0.8. The research provides fundamental insights into how novel chemical bonding can be used to optimize thermoelectric performance in quantum materials. Their work can help to advance the field of green energy production and provide a new direction for the country’s newly launched Quantum Mission.

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