@article{fdi:010060413,
  title = {{L}ow-temperature evolution of {OH} bands in synthetic forsterite, implication for the nature of {H} defects at high pressure},
  author = {{I}ngrin, {J}. and {L}iu, {J}. and {D}epecker, {C}. and {K}ohn, {S}. {C}. and {B}alan, {E}tienne and {G}rant, {K}. {J}.},
  editor = {},
  language = {{ENG}},
  abstract = {{W}e performed in situ infrared spectroscopic measurements of {OH} bands in a forsterite single crystal between -194 and 200 {A} degrees {C}. {T}he crystal was synthesized at 2 {GP}a from a cooling experiment performed between 1,400 and 1,275 {A} degrees {C} at a rate of 1 {A} degrees {C} per hour under high silica-activity conditions. {T}wenty-four individual bands were identified at low temperature. {T}hree different groups can be distinguished: (1) {M}ost of the {OH} bands between 3,300 and 3,650 cm(-1) display a small frequency lowering (< 4 cm(-1)) and a moderate broadening (< 10 cm(-1)) as temperature is increased from -194 to 200 {A} degrees {C}. {T}he behaviour of these bands is compatible with weakly {H}-bonded {OH} groups associated with hydrogen substitution into silicon tetrahedra; (2) {I}n the same frequency range, two bands at 3,617 and 3,566 cm(-1) display a significantly anharmonic behaviour with stronger frequency lowering (42 and 27 cm(-1) respectively) and broadening (similar to 30 cm(-1)) with increasing temperature. {I}t is tentatively proposed that the defects responsible for these {OH} bands correspond to {H} atoms in interstitial position; (3) {I}n the frequency region between 3,300 and 3,000 cm(-1), three broad bands are identified at 3,151, 3,178 and 3,217 cm(-1), at -194 {A} degrees {C}. {T}hey exhibit significant frequency increase (similar to 20 cm(-1)) and broadening (similar to 70 cm(-1)) with increasing temperature, indicating moderate {H} bonding. {T}hese bands are compatible with (2{H})({M}g) defects. {A} survey of published spectra of forsterite samples synthesized above 5 {GP}a shows that about 75 % of the incorporated hydrogen belongs to type (1) {OH} bands associated with {S}i substitution and 25 % to the broad band at 3,566 cm(-1) (type (2); 3,550 cm(-1) at room temperature). {T}he contribution of {OH} bands of type (3), associated to (2{H})({M}g) defects, is negligible. {T}herefore, solubility of hydrogen in forsterite (and natural olivine compositions) cannot be described by a single solubility law, but by the combination of at least two laws, with different activation volumes and water fugacity exponents.},
  keywords = {{F}orsterite ; {H}ydrogen ; {I}nfrared ; {B}and shift ; {O}livine ; {H} defects ; {OH} bands ; {S}ilicon vacancies ; {W}ater solubility laws},
  booktitle = {},
  journal = {{P}hysics and {C}hemistry of {M}inerals},
  volume = {40},
  numero = {6},
  pages = {499--510},
  ISSN = {0342-1791},
  year = {2013},
  DOI = {10.1007/s00269-013-0587-3},
  URL = {https://www.documentation.ird.fr/hor/fdi:010060413},
}