Effective exchange interactions and magnetic phase transition temperatures in Prussian blue analogs: a study by density functional theory

Unrestricted Hartree–Fock and density functional theory (UB2LYP and UB3LYP) calculations using the triple-zeta basis sets were performed in order to elucidate the signs and magnitudes of the effective exchange integrals JMM′ of models of Prussian blue analogs, (NC)5–M–CN–M′–(NC)5 (M=Cr(III), V(II), M′=Cr(III), Mn(II), Ni(II), V(II) and V(III)). Having cyano groups surrounding the transition metal ions is essential for the JMM′ integrals between the transition metal ions. Magnetic phase transition temperatures Tc, estimated from the calculated JMM′ values, correlate linearly with the experimental Tc values.