Metastable structures of solid hydrogen

The J=0{→}2 Raman signal from solid J=0 D₂ or H₂ reveals the hcp structure when deposited at a rate 0.1{≤}R({μ}m/min){≤}40 onto MgF₂ at Td/Tₜₚ{}0.3, a mixture of hcp and fcc crystals at 0.2Td/Tₜₚ0.3 and possibly a randomly stacked close-packed structure at Td/Tₜₚ0.2, where Tₜₚ is the triple point temperature. Non-hcp crystals transform to hcp continuously and irreversibly with increasing T. Finally, the crystal size decreases with decreasing Td and increasing R, from {~}1 mm at Td{~}0.8Tₜₚ and R{~}2 {μ}m/min to {~}1 {μ}m at 0.25 Tₜₚ and R{~}40 {μ}m/min. {} 1996 The American Physical Society.