Pressure and temperature control of spin-switchable metal-organic coordination polymers from ab initio calculations.

We explore a combination of density-functional theory with supplemented Coulomb U (DFT+U) and ab initio molecular dynamics simulations to investigate the spin-crossover (SCO) phenomenon in coordination polymers. We demonstrate the applicability of the method for the case of bimetallic metal-organic framework Fe(2)[Nb(CN)(8)]·(4-pyridinealdoxime)(8)·2H(2)O [see S. Ohkoshi et al. Nat. Chem. 3, 564 (2011)]. Our study shows that this approach is capable of capturing the SCO transitions driven by pressure as well as temperature. In addition to discovering novel spin-state transitions, magnetic states involving changes in the long-range magnetic ordering pattern are achieved, thereby offering the tunability of spin states as well as the long-range order of the spins. We compare the SCO transition in the Fe-based framework with a computer designed Mn-based variant.