New X-ray powder diffraction data for thallium pentaborates Tl[B5O6(OH)(4)]center dot 2H(2)O and TlB5O8

Precise X-ray powder diffraction patterns of hydrated and anhydrous thalliu m pentaborates have been collected on a D5000 diffractometer with a primary monochromated beam (lambda Cu K alpha(1)=1.5406 A). Refinement of indexed reflections led to the following unit cell parameters: a=11.279(1)Angstrom, b=7.1507(6)Angstrom c=13.953(1)A, beta=94.164(7)degrees in the P2(1)/c spa ce group with Z=4, D-x,= 2.713 g cm(-3) D-m,= 2.6 gcm(-3) for Tl[B5O6(OH)(4 )].2H(2)O and a=7.5698(5)Angstrom, b=11.9509(6)Angstrom, c=14.759(1)Angstro m in the Pbca space group with Z=8, D-x,=3.844 gcm-3, D-m,=3.6 g cm(-3) for TlB5O8. Very good Smith and Snyder figures of merit have been obtained: F- 30= 139.7 (0.0043, 50) for Tl[B5O6(OH)(4)].2H(2)O and F-30= 139.3 (0.0054, 40) for TlB5O8. (C) 1999 International Centre for Diffraction Data. [S0885- 7156(98)01504-8].