The role of average atomic volume in predicting negative thermal expansion: The case of REFe(CN)6

Control of Thermal Expansion in TaVO5 by Double Chemical Substitution

“…There are also some materials, although rare, whose volume shrinks with increasing temperature, called negative thermal expansion (NTE) materials . So far, NTE has been reported in many systems such as oxides, − cyanides, − fluorides, − MOFs, and alloys. − But to reach precise volume control and avoid thermal shock, the design of zero thermal expansion (ZTE) materials is fundamental in many technological applications such as high-precision instruments and optical and electronic devices . Some ZTE mechanisms and materials were previously reported, for example, a cage-restricting model in Zn 3 GaB 6 O 12 As and Zn 4 P 6 O 12 S, a guest-molecule steric hindrance effect in TiCo­(CN) 6 ·2H 2 O, local structure distortion in (Sc,Fe)­F 3 , a low-frequency phonon compensation effect in Ta 2 Mo 2 O 11 , O atomic perturbations in Sc 1.5 Al 0.5 W 3 O 12 , spontaneous magnetic ordering related to La 0.5 Ba 0.5 CoO 3– x , and so on.…”

Understanding Large Negative Thermal Expansion of NdFe(CN)6 through the Electronic Structure and Lattice Dynamics

“…Only rarely do some materials show a negative thermal expansion (NTE), and these play an important role since they make possible the realization of materials with zero thermal expansion (ZTE) or even better of materials with tailored thermal expansion . Accordingly, the NTE phenomenon has received great attention and rapid development, such that many NTE materials and mechanisms have been discovered, as reported in recent reviews. − Based on the NTE mechanism, the NTE materials can be grouped into two categories: − electron-driven NTE materials when the NTE is due to magnetic volume effect or charge transfer − and phonon-driven NTE when the presence of low-frequency phonon vibrations gives rise to NTE, ,,,, such as in some oxides, − fluorides, , cyanides, − and MOFs . Open-framework structure materials are excellent candidates for exhibiting phonon-driven NTE, whose origin is often related to the transverse thermal vibration by bridging atoms or the tilting and rotations of atomic polyhedral units.…”

“…), with thermal expansion coefficients α a = −15.4 × 10 −6 K −1 , α c = −10.8 × 10 −6 K −1 , and α v = −41.0 × 10 −6 K −1 in the temperature range investigated. Compared with the most popular NTE materials such as ZrW 2 O 8(α v = −26.1 × 10 −6 K −1 , 0.3−1050 K), 1 ScF 3 (α l = −12.3 × 10 −6 K −1 , 10− 1010 K),18 and β-Cu 1.8 Zn 0.2 V 2 O 7 (α l = −14.4 × 10 −6 K −1 , 100−700 K),51 NdFe(CN) 6 has a larger NTE magnitude, albeit in a narrower temperature range. However, compared among the PBAs such as FeCo(CN) 6 (ΔT = 296 K),52 MPt(CN) 6 (ΔT = 300 K),34 M 3 [B(CN) 6 ] 2 (ΔT = 175 K),53 …”

Insight into the Relationship between Negative Thermal Expansion and Structure Flexibility: The Case of Zn(CN)2-Type Compounds

“…3,10,26,27 This can be related to the different lattice parameters attributed to the diverse ion or atomic radius, which makes the structural flexibility of the system different, resulting in a different NTE coefficient. 27,28 However, the relationship between structural flexibility (therefore of AAV) and NTE deserves further investigation. Indeed, in the ZrW 2 O 8 series, slight differences in the AAV give rise to significant changes in the NTE coefficient, while in Zn(CN) 2 and Cd(CN) 2 compounds, large differences of AAV give small changes in the NTE.…”