Gadolinium high-spin diatomics with first-and second-row elements of groups 15᎐17 as well as the gadolinium dimer were studied by fully relativistic density functional and scalar relativistic ab initio pseudopotential configuration interaction calculations. Bond lengths, binding energies, vibrational frequencies, dipole moments, and charge distributions are presented for the ground and low-lying excited states. In addition, the different contributions of the 4 f shell to chemical bonding in wavefunction-based and density-based calculations are investigated.

A joint experimental and theoretical investigation of the spin 1/2 system Cu 2 ͑PO 3 ͒ 2 CH 2 suggests a description of this compound as coupled alternating antiferromagnetic Heisenberg chains. Magnetic susceptibility, specific heat, nuclear magnetic resonance, nuclear quadrupole resonance, and high-field magnetization measurements evidence a spin gap of about 25 K. Surprisingly, the leading antiferromagnetic exchange of about 75 K can be assigned by density-functional band-structure calculations to a coupling between the structural Cu 2 O 6 dimers, whereas the coupling within these dimers is strongly reduced due to sizable ferromagnetic contributions. The coupling within the structural dimers competes with a number of long-range couplings. The present available experimental data can be consistently described in a scenario of coupled alternating chains. The proposed model should be considered as a minimal model for an appropriate description of this compound.

Based on electronic structure calculations within the density functional theory, we report a systematic approach for the modelling of low-dimensional Cu II materials. Combining concepts of crystal chemistry with ab initio-based magnetic models, we present a systematic study of recently discovered compounds. Our calculation results are in good agreement with thermodynamic and magnetic measurements, suggesting the presented approach as a well-directed route to explore the magnetic phase diagram of low-dimensional Cu II systems.