data_global
_chemical_name_mineral 'Protopyroxene'
loop_
_publ_author_name
'Yang H'
'Finger L W'
'Conrad P G'
'Prewitt C T'
'Hazen R M'
_journal_name_full 'American Mineralogist'
_journal_volume 84 
_journal_year 1999
_journal_page_first 245
_journal_page_last 256
_publ_section_title
;
 A new pyroxene structure at high pressure: Single-crystal X-ray and Raman study
 of the Pbcn - P2_1cn phase transition in protopyroxene
 Sample at P = 9.98 GPa, (Mg1.54Li.23Sc.23)Si2O6
;
_database_code_amcsd 0002099
_chemical_formula_sum '(Mg1.54 Sc.23) Li.23 Si2 O6'
_cell_length_a 8.9921
_cell_length_b 8.6310
_cell_length_c 5.0659
_cell_angle_alpha 90
_cell_angle_beta 90
_cell_angle_gamma 90
_cell_volume 393.169
_exptl_crystal_density_diffrn      3.405
_symmetry_space_group_name_H-M 'P 21 c n'
loop_
_space_group_symop_operation_xyz
  'x,y,z'
  'x,-y,1/2+z'
  '1/2+x,1/2+y,1/2-z'
  '1/2+x,1/2-y,-z'
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_occupancy
_atom_site_U_iso_or_equiv
Mg1   0.00000   0.09680   0.70870   0.77000   0.00646
Sc1   0.00000   0.09680   0.70870   0.23000   0.00646
Mg2   0.01270   0.26640   0.20900   0.77000   0.00861
Li2   0.01270   0.26640   0.20900   0.23000   0.00861
SiA   0.70160   0.91010   0.85450   1.00000   0.00557
SiB   0.30060   0.08840   0.06690   1.00000   0.00481
O1A   0.87970   0.91040   0.86920   1.00000   0.00735
O1B   0.12270   0.08330   0.05400   1.00000   0.00583
O2A   0.62390   0.76050   0.96230   1.00000   0.00469
O2B   0.37410   0.24980   0.11090   1.00000   0.00874
O3A   0.64350   0.94550   0.55170   1.00000   0.00760
O3B   0.36330   0.95760   0.27190   1.00000   0.00367