  The sound velocity of some liquid elements of groups IV, V and VI, as
reported in the literature, displays anomalous features that set them apart
from other liquid metals. In an effort to determine a possible common origin of
these anomalies, extensive neutron diffraction measurements of liquid Bi and Sb
were carried out over a wide temperature range. The structure factors of liquid
Sb and Bi were determined as a function of temperature. The structure of the
two molten metals was carefully analyzed with respect to peak locations, widths
and coordination number in their respective radial distribution function. The
width of the peaks in the radial distribution function were not found to
increase and even decreased within a certain temperature range. This anomalous
temperature dependence of the peak widths correlates with the anomalous
temperature dependence of the sound velocity. This correlation may be accounted
for by increasing rigidity of the liquid structure with temperature. A
phenomenological correlation between the peak width and the sound velocity is
suggested for metallic melts and is found to agree with available data for
normal and anomalous elemental liquids in groups IV-VI.
