NaAlSi is an sp electron superconductor crystallizing in a layered structure of the anti-PbFCl type with a relatively high transition temperature Tc of ~7 K. Recent electronic state calculations re...

Tin‐based intermetallics with tunnel frameworks containing zigzag Na chains that excite correlated rattling impinging on the framework phonons are attractive as thermoelectric materials owing to their low lattice thermal conductivity. The correlated rattling of Na atoms in the zigzag chains and the origin of the low thermal conductivity is uncovered via experimental and computational analyses. The Na atoms behave as oscillators along the tunnel, resulting in substantial interactions between Na atoms in the chain and between the chain and framework. In these intermetallic compounds, a shorter inter‐rattler distance results in lower thermal conductivity, suggesting that phonon scattering by the correlated rattling Na‐chains is enhanced. These results provide new insights into the behavior of thermoelectric materials with low thermal conductivity and suggest strategies for the development of such materials that utilize the correlated rattling.

Rate coefficients are reported for the gas-phase reaction of the hydroxyl radical (OH) with 1,1-dichloroethylene (k₁) and trans-1,2-dichloroethylene (k₂) over an extended temperature range at 740 ± 10 Torr in a He bath gas. Absolute rate measurements were obtained using a laser photolysis/laser-induced fluorescence (LP/LIF) technique under slow flow conditions. Rate measurements for k₁ exhibited complex behavior with negative temperature dependence at temperatures below 640 K, a rapid falloff in rate between 650 and 700 K, and positive temperature dependence from 700 to 750 K. The simple Arrhenius equation adequately describes the data below 640 K and above 700 K and is given (in units of cm³ molecule^-1 s^-1) by k₁(291−640 K) = (1.81 ± 0.36) × 10^-12 exp(511 ± 71)/T and k₁(700−750 K) = 3.13 × 10^-10 exp(−5176/T). Rate measurements for k₂ also exhibited complex behavior with a near-zero or slightly negative temperature dependence below 500 K and a near-zero or slightly positive temperature dependence above 500 K. The modified Arrhenius equation adequately describes all of the data and is given (in units of cm³ molecule^-1 s^-1) by k₂(293−720 K) = (9.75 ± 1.14) × 10^-18 T^{1.73± 0.05} exp(727 ± 46)/T. Error limits are 2σ values. The room-temperature values for k₁ and k₂ are within ±2σ of previous data using different techniques. The rate measurements were modeled using QRRK theory. OH addition to the unsubstituted carbon followed by adduct stabilization describes the low-temperature measurements for k₁. Analysis of equilibration in this system yields a C−O bond dissociation enthalpy of 32.8 ± 1.5 kcal mol^-1 at 298 K, a value confirmed by ab initio calculations. OH addition followed by Cl elimination described the experimental data for k₂. Ab initio based transition state calculations for the H atom abstraction channel indicated that this mechanism is consistent with the rate measurements for k₁ above 700 K. The H abstraction channel for k₂ could not be observed because of the presence of a more rapid Cl elimination channel at elevated temperatures. H abstraction is predicted to be the dominant reaction channel for both k₁ and k₂ at flame temperatures.