Single-crystal structural investigation of BaO2

Structural Properties of Nonstoichiometric Barium and Strontium Peroxides: BaO2−x (1.97≥2−x≥1.72) and SrO2−x (1.98≥2−x≥1.90)

“…Furthermore, in neither of these studies was it possible to prove the presence of oxide ions in the crystal lattice, as is required for nonstoichiometric compounds. Moreover, we have the single crystal X-ray study by Wong-Nog et al (6), which suggests a stoichiometric composition for barium peroxide. In view of this uncertainty, we have undertaken a systematic study of several single crystals of barium and strontium peroxide to clarify the questions concerning the nonstoichiometry in these materials.…”

“…1: the peroxide dumbbells (O\ ) are aligned along the c-axis, and replacing some of them by the smaller, oxygen content of the nonstoichiometric barium peroxide, and Table 4 gives, for the "ve barium peroxide single crystals, a concise summary of some of the most important results of the X-ray investigations and demonstrates also that the c-axis and the peroxide bond length decrease with a decreasing peroxide content or a decreasing total oxygen content. Finally, we compare the results for the nonstoichiometric barium peroxide crystals with those of the single crystal X-ray study of VerNooy (4) and those of Wong-Ng et al (6). The results of VerNooy (a"3.8016(4) A s , c"6.7786 (8) , because we would expect a c-axis of 6.873 A s for the stoichiometric compound (Fig.…”

Ab InitioQuantum Mechanical Study of the Structure and Stability of the Alkaline Earth Metal Oxides and Peroxides

“…The main features of the early structural models for these two peroxides proposed by Bernal et al (1) are based on powder diffraction data; they were recently confirmed by single crystal X-ray diffraction (2)(3)(4), although the peroxide bond lengths found…”

Phase diagrams for the YBa2Cu3O7 family — ANNO 1996

“…In a further investigation of the crystal structure [145], a determination was attempted for the orientation of the carbonate groups in a single-phase material {/4; 780.5, 1499.3}. The same structure [146] is obtained by replacing, say, 20% of the carbonate groups by borate, {/4; 778.81 (15), 1496.8(3)}. Above some 220"C, a structural transition is observed {P4212; 554.36(1), 753.82(1)} [147].…”

“…This should be taken into consideration in the evaluation of the oxygen dissociation pressure, which will vary with the content of peroxide in the solid-solution phase [13]. To illustrate rough trends, equilibrium oxygen pressures for SrO1.97 [12], and for the oxide-saturated barium peroxide are expressed (p in Pa, Tin K) [12,13] The peroxides crystallize [14,15] with the CaC2-type structures: CaO2 {P4/mmm; 356, 596} [16], SrOz {355,655} [17] and BaO2 {381.14(6), 682.15(11)} [15].…”