文摘
All-atom molecular dynamics simulations have been carried out to investigate orientation jumps of acetamide molecules in three different ionic deep eutectics made of acetamide (CH3CONH2) and lithium salts of bromide (Br鈥?/sup>), nitrate (NO3鈥?/sup>) and perchlorate (ClO4鈥?/sup>) at approximately 80:20 mole ratio and 303 K. Orientational jumps have been dissected into acetamide鈥揳cetamide and acetamide鈥搃on catagories. Simulated jump characteristics register a considerable dependence on the anion identity. For example, large angle jumps are relatively less frequent in the presence of NO3鈥?/sup> than in the presence of the other two anions. Distribution of jump angles for rotation of acetamide molecules hydrogen bonded (H-bonded) to anions has been found to be bimodal in the presence of Br鈥?/sup> and is qualitatively different from the other two cases. Estimated energy barrier for orientation jumps of these acetamide molecules (H-bonded to anions) differ by a factor of 鈭? between NO3鈥?/sup> and ClO4鈥?/sup>, the barrier height for the latter being lower and 鈭?.5kBT. Relative radial and angular displacements during jumps describe the sequence ClO4鈥?/sup> > NO3鈥?/sup> > Br鈥?/sup> and follow a reverse viscosity trend. Jump barrier for acetamide鈥揳cetamide pairs reflects weak dependence on anion identity and remains closer to the magnitude (鈭?.7kBT) found for orientation jumps in molten acetamide. Jump time distributions exhibit a power law dependence of the type, P(tjump) 鈭?A(tjump/蟿)鈭捨?/sup>, with both 尾 and 蟿 showing substantial anion dependence. The latter suggests the presence of dynamic heterogeneity in these systems and supports earlier conclusions from time-resolved fluorescence measurements.