Exchange Interactions in a Low-Dimensional Magnetic System $Cu(H_{2}O)_{2}(en)SO_{4}$

We report a theoretical ab-initio investigation of the exchange interaction between Cu atoms in $Cu(H_{2}O)_{2}(en)SO_{4}$, en=$C_{2}H_{8}N_{2}$(ethylenediamine), an insulating magnetic material. Unlike previous experimental studies which describe the system as a quasi-two-dimensional antiferromagnet, our results, based on the mapping of the system onto an effective Heisenberg model, suggest a quasi-one-dimensional character of magnetism, with the exchange coupling between the Cu atoms being propagated along a zigzag line, lying in the crystal's bc plane and connecting the Cu atoms through the N atoms. Furthermore, we report the calculated positions of the H atoms that have not been provided in experimental papers.