The crystal structures of solid Cl2 for Cmca (a), bco (b), and fcc (c) phases. The unit cells for each phase are indicated by rectangles. The atoms shown in grey are lying in the x = 1/2 plane.
(a)-(d) are the oF28, oF20, oC12, and oC20 structures of solid Cl2 predicted by the CALYPSO simulation at 150 GPa, respectively. (e) is the basic fco structural unit and (f) is the modulated fco having a Cmcm symmetry with a modulation wave vector k = 1/4 for solid I2. The figures show the projection of atoms into the planes indicated. The unit cells for each phase are indicated by rectangles. The atoms shown in brown or grey are lying in the plane or in the adjacent plane being halfway below.
Enthalpy curves (relative to the bco structure) for various structures indicated as a function of pressure in pressure ranges of 130–180 GPa (a) and 120–400 GPa (b). Note that the energy convergence better than 0.5 meV/atom in our calculation allowed us to derive a reliable conclusion on the phase stability of oF28 over other phases since energy differences between oF28 and other structures are typically larger than 0.5 meV/atom.
(a) X-ray diffraction pattern (with the x-ray wavelength of 0.4264 Å) of our predicted oF28 structure at 150 GPa. The asterisks indicate the fco peaks at 150 GPa. For comparison, the inset shows the experimental diffraction profile from Ref. 17 for incommensurate phase V of iodine at 24.6 GPa.
The pressure dependence of Raman active modes for molecular Cmca phase. There are two Raman active stretching (, ) modes and two Raman librational (, ) modes, whose vibrational patterns are indicated.
Calculated total and partial density of states of Cmca at 50 GPa (a), oF28 at 150 GPa (b), bco at 200 GPa (c), and fcc at 400 GPa (d), respectively. Vertical dashed lines indicate the Fermi level.
Pressure dependence of calculated T c and λ for bco and fcc phases. Left and right vertical ordinates are for T c and λ, respectively.
Structural parameters for various modulated structures at 150 GPa.
Article metrics loading...
Full text loading...