Extreme Anharmonicity and Thermal Contraction of One-Dimensional Wires.

Ultrathin nanowires could play a central role in next-generation downscaled electronics. Here, we explore some of the most promising candidates identified from previous high-throughput screening─CuC2, TaSe3, and AuSe2─to gain insight into the thermodynamic and anharmonic behaviors of nanowires that could be exfoliated from weakly bonded three-dimensional materials. We analyze thermal stability, linear thermal expansion, and anharmonic heat capacity using the stochastic self-consistent harmonic approximation. Notably, our work unveils exotic features common among all one-dimensional wires: a colossal record negative thermal expansion and very large deviations from the Dulong-Petit law due to strong anharmonicity.