Connecting electronic entropy to empirically accessible electronic properties in high temperature systems

Abstract

A quantitative theoretical model connecting the thermopower and electronic entropy of molten systems is proposed, the validity of which is tested for semiconductors and metallic materials. The model accurately provides the entropy of mixing for molten semiconductors, as shown for the representative system Te–Tl. Predictions of the electronic entropy of fusion for compounds are in agreement with available data and offer a novel means to identify the correct electrical conductivity model when Hall measurements are not available. Electronic entropy for molten semiconductor and metallic systems is shown to reflect order in the molten and solid state. The model proves accurate at predicting the electronic state entropy contribution to the electronic entropy of mixing.

Keywords:

• Entropy
• electronic entropy
• thermopower
• molten semiconductor

Acknowledgements

We would like to acknowledge the role of the Fannie and John Hertz Foundation for support of the researchers and Dr. Ali Sayir and the AFOSR for their financial support.

Notes

1. For systems that exhibit ambipolar conductivity a similar equation with contributions from both electrons and holes is used. We simplify for purpose of demonstration to systems that exhibit monopolar conductivity.

2. For a discussion on the validity of decomposing the free energy function into components see Smith [34].

3. Mechanical mixing entropy is the concentration-weighted entropies of the end members of a system in absence of any chemical interactions. Thermodynamic mixing functions are referenced to mechanical mixing: ΔX_mix = X – X^m.