Cu^II materials—From crystal chemistry to magnetic model compounds

Abstract

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.

Reply to Comment on ‘Oxygen vacancy-induced magnetic moment in edge-sharing CuO2 chains of Li2CuO2-δ ’

“…Since Li has a high electron affinity, making the occurrence of electron sharing with its neighboring oxygen unlikely, a molecular model of the implied interchain exchange coupling through the Cu-O-Li-O-Cu super-superexchange route for Li CuO 2 2 is purely imaginary, though it is often assumed as that depicted in figure 1 of Lorenz 2009, where the ionic bond of the electron donation has extended to σ-bond-type electron sharing for the electron/spin exchange interaction. Similar chemical bond models for the chain and layered compounds, such as Na CoO x 2 and TiSe 2 have been proposed before [18,19], as also noted by Rosner et al regarding the intimate relationship between crystal chemistry and magnetism [20]. Although the MDD interaction is relatively weak compared to that of the spin exchange interaction [17], it becomes non-negligible once the dimension is taken into consideration, which is similar to the character of the van der Waals force of the electric dipole interaction between large areas of layers for most van der Waals materials.…”

Dimers of oxocentred [OCu4]6+ tetrahedra in two novel copper selenite chlorides, K[Cu3O](SeO3)2Cl and Na2[Cu7O2] (SeO3)4Cl4, and related minerals and inorganic compounds

“…THE crystal chemistry of selenium-containing natural and synthetic oxocompounds of copper is of special interest owing to the specific structural features of both Cu 2+ and Se 4+ ions. Cu 2+ may possess different and flexible coordination geometries (Burns and Hawthorne, 1995a,b;Rosner et al, 2007;Melník et al, 2011;Burrows et al, 2012;Krivovichev et al, 2012), while Se 4+ cations form asymmetric (SeO 3 ) 2groups due to the stereochemically active behaviour of the s 2 lone electron pairs, resulting in structurally complex architectures and interesting physical properties (Mao et al, 2008;Zhang et al, 2010;Berdonosov et al, 2013).…”

Synthesis, Crystal Structure, and Physical Properties of BaAg2Cu[VO4]2: A New Member of the S = 1/2 Triangular Lattice

“…3 Lately, conclusions drawn from experimental work, mainly magnetization and specific heat measurements, have received extensive theoretical support by band structure calculations based on density functional theory (DFT), mapping the relevant local density approximation (LDA) bands onto a tight binding (TB) model and subsequently onto a Hubbard and Heisenberg model. 4 Examples for one-dimensional (1D) spin systems following the behavior of a Heisenberg antiferromagnet (H = J intra P i S i 3 S iþ1 ) in a wide temperature range are, for example, AgCuVO 4 (SE, J intra ≈ 330 K) 5 and Ba 2 Cu[PO 4 ] 2 (SSE, J intra = 151(6) K). 6 At low temperatures interchain correlations often lead to long-range magnetic order, with T N = 2.5 K in the first case, but were not observed for the latter compound down to temperatures as low as 0.45 K. Many phosphates have been studied yielding a consistent picture of the exchange parameter, J intra , relating to a SSE pathway, whereas a few cuprates consisting of solely vanadate bridging features have been studied in detail so far.…”

“…In recent years it has been established that not only superexchange (SE) pathways as described by Goodenough can be the dominating magnetic nearest neighbor interaction, but also super-super exchange (SSE) via phosphates and vanadates is likely to play a major role in the evaluation of low-dimensional magnetic properties . Lately, conclusions drawn from experimental work, mainly magnetization and specific heat measurements, have received extensive theoretical support by band structure calculations based on density functional theory (DFT), mapping the relevant local density approximation (LDA) bands onto a tight binding (TB) model and subsequently onto a Hubbard and Heisenberg model . Examples for one-dimensional (1D) spin systems following the behavior of a Heisenberg antiferromagnet ( H = J intra ∑ i S i · S i +1 ) in a wide temperature range are, for example, AgCuVO 4 (SE, J intra ≈ 330 K) and Ba 2 Cu[PO 4 ] 2 (SSE, J intra = 151(6) K) .…”