Effect of the variation of the bond length on laser-induced spin-flip scenarios atNi 2 D. Chaudhuri 1* , G. Lefkidis 1 , A. Kubas 2 , K. Fink 3 , W. Hübner 1 1 Dept. of Physics and Research Center OPTIMAS, University of Kaiserslautern, Germany 2 Department of Physics and Astronomy, University College London, UK 3 Institute of Nanotechnology, Karlsruhe Institute of Technology, Germany chaudhuri@physik.uni-kl.de Abstract We investigate laser-induced spin-dynamics scenarios on a nickel dimer at various interatomic distances. Successful spin-flip processes based on highly correlated abinitio calculations are established and analyzed. Switching is achieved through a laser-driven Λ-process and optimized with a genetic algorithm. Introduction Theoretical[1,2] and experimental[3] treatment of transition metals attract growing interest since the last decade because of their complex electronic and magnetic properties. Nickel is interesting to investigate because of its open  subshells which lead to complicated electronic structures. Bonding in Ni 2 molecule is main- ly due to 4s orbitals interaction with only small 3d-3d contribution due to their strongly localized character.Ultrafast dynamics[4-6] is particularly important in order to meet the industrial necessities that demand for smaller sizes and shorter time scales with respect to magnetic responses in spintronic devices. Results and Discussion We describe our system with two real-space quantum chemistry methods: the equation-of-motion coupled-cluster with single and double excitations (EOM- CCSD [7] in the GAUSSIAN09 package [8]), and the-electron valence-state per- turbation theory (NEVPT2[9] in the ORCA package [10], Fig. 1) based on CAS (20, 12) with all 3d and 4s orbitals in the active spaceand scalar relativistic effects at the DKH2 level [11].We take four steps:(a) computation of the ground and the 30 lowest excited states,(b) perturbative inclusion of spin-orbit coupling(SOC),(c) Ó Springer International Publishing Switzerland 2015 J.-Y. Bigot et al. (eds), Ultrafast Magnetism I, Springer Proceedings in Physics 159 DOI 10.1007/978-3-319-07743-7_51 159