Abstract:
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A wide range of experimental, semiempirical, and theoretical values have been reported in the literature for
the magnetic coupling parameters of the two-leg ladder compound SrCu2O3. We apply quantum chemical and
density functional techniques to calculate accurate N-electron wave functions or densities for two different
Cu2O7 clusters that represent the leg (Ji) and rung (J') of the ladder. Our data indicate that Ji is slightly larger
than J' (J' /Ji'0.9) with J'52139 meV ~21670 K! and Ji52156 meV ~21870 K!. Recent experimental
data indicate a more strongly anisotropic ratio, J' /Ji'0.5. The origin of the difference is unclear, as our ab
initio estimates of J' and Ji seem to be converged with respect to the size of the basis set, the level of electron
correlation, and the size of the cluster. However, we also find a surprisingly strong ferromagnetic interladder
interaction which may play a role in resolving this discrepancy. |