Zhang Yachao
Guizhou Provincial Key Laboratory of Computational Nano-Material Science, Guizhou Education University, Guiyang 550018, China.
Materials (Basel). 2023 Sep 10;16(18):6150. doi: 10.3390/ma16186150.
It is essential that one understands how the surface degrees of freedom influence molecular spin switching to successfully integrate spin crossover (SCO) molecules into devices. This study uses density functional theory calculations to investigate how spin state energetics and molecular vibrations change in a Fe(II) SCO compound named [Fe(py)bpym(NCS)] when deposited on an Al(100) surface. The calculations consider an environment-dependent to assess the local Coulomb correlation of 3d electrons. The results show that the adsorption configurations heavily affect the spin state splitting, which increases by 10-40 kJmol-1 on the surface, and this is detrimental to spin conversion. This effect is due to the surface binding energy variation across the spin transition. The preference for the low-spin state originates partly from the strong correlation effect. Furthermore, the surface environment constrains the vibrational entropy difference, which decreases by 8-17 Jmol-1K-1 (at 300 K) and leads to higher critical temperatures. These results suggest that the electronic energy splitting and vibrational level shifting are suitable features for characterizing the spin transition process on surfaces, and they can provide access to high-throughput screening of spin crossover devices.
要成功地将自旋交叉（SCO）分子集成到器件中，了解表面自由度如何影响分子自旋切换至关重要。本研究使用密度泛函理论计算来研究一种名为[Fe(py)bpym(NCS)]的Fe(II) SCO化合物沉积在Al(100)表面时自旋态能量学和分子振动如何变化。计算考虑了一种依赖于环境的情况，以评估3d电子的局部库仑相关性。结果表明，吸附构型严重影响自旋态分裂，在表面上自旋态分裂增加了10 - 40 kJmol-1，这对自旋转换不利。这种效应是由于自旋转变过程中表面结合能的变化。对低自旋态的偏好部分源于强相关效应。此外，表面环境限制了振动熵差，在300 K时振动熵差降低了8 - 17 Jmol-1K-1，并导致更高的临界温度。这些结果表明，电子能量分裂和振动能级移动是表征表面自旋转变过程的合适特征，它们可以为自旋交叉器件的高通量筛选提供途径。
