x-[Pd(dmit)2]2 as a quasi-one-dimensional scalene Heisenberg model

From first principles, we calculate the Heisenberg interactions between neighboring dimers in several compounds within the EtnMe4-nX[Pd(dmit)(2)](2) (Et = ethyl, Me = methyl, dmit = 2-thioxo-1,3-dithiole-4,5-dithiolate) family using an atomistic approach, with broken-symmetry density functional theory. In all materials, we find a scalene triangular model where the strongest exchange coupling along one crystallographic axis is up to three times larger than the others and where the frustration further enhances this quasi-one-dimensionality. We calculate the Neel ordering temperature via the chain random phase approximation. We show that the difference in the frustrated interchain couplings is equivalent to a single bipartite interchain coupling, favoring long-range magnetic order. We find that the Neel ordering temperatures are the same order of magnitude as the experimentally measured values for most compounds.