SYNTHESIS, STRUCTURE, AND PROPERTIES OF THE NONCENTROSYMMETRIC PYROBORATE BACUB2O5

The new noncentrosymmetric pyroborate BaCuB2O5 has been synthesized an d its structure determined by single-crystal X-ray methods. It crystal lizes in the monoclinic space group C2 with a cell of dimensions a=6.4 85(1), b=9.165(1), c=3.971(1) Angstrom, and beta=96.14(1)degrees. The structure was determined from 1281 unique reflections and refined to t he final residuals R=0.039 and wR=0.049. It is composed of highly dist orted [CuO4] squares and double-triangular [B2O5] groups that are conn ected to form infinite two-dimensional layers. The layers are stacked parallel to (001), and the Pa atoms interleave successive layers. Para llel alignment of the pyroborate groups is conductive to high efficien cy for optical frequency conversion. The magnetic moment at 22 degrees C is 1.69+/-0.03 mu(B). (C) 1997 Academic Press.