Magnetic exchange interactions in alpha-RuCl3: ab initio study.

We study the magnetic exchange interactions in alpha-RuCl3, a promising candidate of the Kitaev quantum spin liquid, by density functional theory calculation based on the newly reported rhombohedral crystal structure (R-3). By precisely mapping the total energies of constrained non-collinear spin configurations into the Kitaev-Heisenberg Hamiltonian, we have obtained various isotropic and anisotropic interaction parameters of the zigzag magnetic order. Our calculation reveals the importance of further neighbor anisotropic and interlayer interactions to stabilize the zigzag-type antiferromagnetic order as a ground state of the system. Comparison with previous studies are also made.