Trends in Siting of Metals in Heterometallic Nd–Yb Metal–Organic Frameworks and Molecular Crystals

Several studies suggest that metal ordering within metal–organic
frameworks (MOFs) is important for understanding how MOFs behave in
relevant applications; however, these siting trends can be difficult
to determine experimentally. To garner insight into the energetic
driving forces that may lead to nonrandom ordering within heterometallic
MOFs, we employ density functional theory (DFT) calculations on several
bimetallic metal–organic crystals composed of Nd and Yb metal
atoms. We also investigate the metal siting trends for a newly synthesized
MOF. Our DFT-based energy of mixing results suggest that Nd will likely
occupy sites with greater access to electronegative atoms and that
local homometallic domains within a mixed-metal Nd–Yb system
are favored. We also explore the use of less computationally extensive
methods such as classical force fields and cluster expansion models
to understand their feasibility for large system sizes. This study
highlights the impact of metal ordering on the energetic stability
of heterometallic MOFs and crystal structures.