title: Like Charges Attract?
abstract: Using multiscale first-principles calculations, we show that two interacting negatively charged B12I9(-) monoanions not only attract, in defiance of the Coulomb's law, but also the energy barrier at 400 K is small enough that these two moieties combine to form a stable B24I18(2-) moiety. Ab initio molecular dynamics simulations further confirm its stability up to 1500 K. Studies of other B12X9(-) (X = Br, Cl, F, H, Au, CN) show that while all of these B24X18(2-) moieties are stable against dissociation, the energy barrier, with the exception of B24Au18(2-), is large so as to hinder their experimental observation. Our results explain the recent experimental observation of the "spontaneous" formation of B24I18(2-) in an ion trap. A simple model based upon electrostatics shows that this unusual behavior is due to competition between the attractive dipole-dipole interaction caused by the aspherical shape of the particle and the repulsive interaction between the like charges.
authors.affiliation: Center for Applied Physics and Technology, College of Engineering, Peking University, Key Laboratory of High Energy Density Physics Simulation, and IFSA Collaborative Innovation Center, Ministry of Education , Beijing 100871, China.|Department of Physics, Virginia Commonwealth University , Richmond, Virginia 23284, United States.
authors.forename: Tianshan
authors.initials: T
authors.lastname: Zhao
authors.affiliation: Department of Physics, Virginia Commonwealth University , Richmond, Virginia 23284, United States.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Center for Applied Physics and Technology, College of Engineering, Peking University, Key Laboratory of High Energy Density Physics Simulation, and IFSA Collaborative Innovation Center, Ministry of Education , Beijing 100871, China.|Department of Physics, Virginia Commonwealth University , Richmond, Virginia 23284, United States.
authors.forename: Qian
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Department of Physics, Virginia Commonwealth University , Richmond, Virginia 23284, United States.
authors.forename: Puru
authors.initials: P
authors.lastname: Jena