Influence of A/B Element Substitution on Negative Thermal Expansion in AB(CN)₆ (A = Al, Ga, In; B = Co, Fe, Mn, Cr, V, Ti): A Density Functional Theory Study

Abstract

Negative thermal expansion as an abnormal physical behavior of materials has promising applications in a high sophisticated equipment field, but the materials are rare. Here, we use the first-principles calculations based on density functional theory combined with the recently developed average atomic volume (AAV = V/N, where V is unit cell volume and N is the number of atoms in the unit) rule to predict the large isotropic negative thermal expansion materials of Prussian blue analogues AB(CN) 6 (A = Al, Ga, In; B = Co, Fe, Mn, Cr, V, Ti) in a wide temperature range. Our results clearly show that the coefficient of negative thermal expansion has a near-linear relationship with the average atomic volume of the systems and is also influenced by the element substitution at the A or B site. Lattice dynamic simulations indicate that the main contribution to the negative thermal expansion comes from the low-frequency transverse vibration of the (B)−C�N−(A) groups, especially the transverse vibration of the N atoms. Thus, the element substitution at the A site (binding to N) can tune the negative thermal expansion behavior of the systems more effectively than that at the B site (binding to C), indicating the different roles of bonds on the negative thermal expansion. Our present work not only expands the kinds of isotropic materials but also gives some insights into the relationship between the average atomic volume and negative thermal expansion.

Critical Role of Nonrigid Unit and Spiral Acoustical Modes in Designing Colossal Negative Thermal Expansion

“…Thermal expansion is a fundamental property of materials, and controlling it presents a challenging yet crucial issue with significant industrial and technological implications . In recent years, there has been growing interest in negative thermal expansion (NTE) materials due to their potential for mitigating thermal expansion in matrix materials. − To date, fewer than 150 types of NTE materials have been identified, including open-framework materials such as oxides, , Prussian blue analogs, − fluorides , and MOFs . NTE has also been observed in some nanosolids and 2D materials, , and often coinciding with other functional properties, such as magnetism, ferroelectricity, phase changes, charge density waves, and charge transfer phenomena. − However, understanding the mechanism behind NTE is complex, involving interactions between phonons, electrons, spin and orbitals.…”