Low-Energy Linear Structures in Dense Oxygen: Implications for the   $\epsilon$-phase
  Using density functional theory implemented within the generalized gradient approximation, a new non-magnetic insulating ground state of solid oxygen is proposed and found to be energetically favored at pressures corresponding to the $\epsilon$-phase. The newly-predicted ground state is composed of linear herringbone-type chains of O$_2$ molecules and has {\it Cmcm} symmetry (with an alternative monoclinic cell). Importantly, this phase supports IR-active zone-center phonons, and their computed frequencies are found to be in broad agreement with recent infrared absorption experiments. 
J. B. Neaton (Rutgers University) and N. W. Ashcroft (University of   Cambridge, Cornell University)