Exploring Combined Stereochemically Active Lone-Pair and Rattling Effects in Thermoelectrics with Machine Learning
Harpriya Minhas1, Rahul Kumar Sharma1, Biswarup Pathak1
1Department of Chemistry, Indian Institute of Technology (IIT) Indore, Indore, Madhya Pradesh 453552, India.
The Journal of Physical Chemistry Letters
|May 13, 2025
Summary
Stereochemically active lone pairs (SCALPs) and rattling atoms significantly impact thermoelectric materials. Machine learning potentials reveal their combined effects in AAsSe2, reducing thermal conductivity through enhanced phonon scattering.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Computational Chemistry
Background:
- Stereochemically active lone pairs (SCALPs) break symmetry and influence thermoelectric properties.
- Rattling atoms disrupt phonon transport, affecting thermal conductivity.
- Calculating thermal transport in noncentrosymmetric structures with SCALPs and rattling atoms is challenging for ab initio methods.
Purpose of the Study:
- To investigate the combined effects of SCALPs and rattling atoms on thermoelectric properties in AAsSe2 (A = Li or Na).
- To utilize machine learning interatomic potentials (MLIPs) for exploring these complex interactions.
- To understand the underlying mechanisms of anharmonicity and phonon scattering in these materials.
Main Methods:
- Employing machine learning interatomic potentials (MLIPs) for simulations.
- Analyzing the structural and vibrational properties of AAsSe2 systems.
- Investigating the role of SCALPs (specifically As 4s^2) and rattling atoms in inducing anharmonicity.
Main Results:
- Identified strong anharmonicity in γ-NaAsSe2 due to rattling modes and As 4s^2 SCALP-induced electrostatic interactions.
- Observed reduced lone-pair angles and unique chemical bonding involving antibonding states.
- Demonstrated that rattler atom vibrations, phonon softening, structural distortions, and enhanced phonon scattering contribute to high anharmonicity.
Conclusions:
- SCALPs and rattling atoms synergistically enhance anharmonicity and phonon scattering in AAsSe2 materials.
- MLIPs are effective tools for studying complex thermoelectric materials.
- This research accelerates the design of advanced thermoelectric materials by understanding these combined effects.
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