Phk. Dejong et al., NEUTRON-DIFFRACTION STUDY OF LIQUID LIXSI1-X ALLOYS WHERE X=0.80, 0.65 AND 0.57, Journal of physics. Condensed matter, 7(3), 1995, pp. 499-516
We report a neutron diffraction experiment on liquid 7LixSil-x alloys
(x = 0.80, 0.65 and 0.57) just above the liquidus and on 7Li57Si43 at
about 200 K above the liquidus. We obtained absolutely normalized and
fully corrected structure factors and radial distribution functions, w
hich provide indications for the occurrence of chemical ordering in al
l three alloys. We have analysed the data by fitting models to the str
ucture factor and to the radial distribution function, and by using th
e reverse Monte Carlo (RMC) method. We find strong indications for the
presence of covalently bonded Si in liquid Li65Si35 and Li57Si43. The
Si-Si coordination number Z(SiSi) varies from about 1.5 in Li65Si35 t
o about 2 in Li57Si43. For c(Si) > 0.2, Si forms poly-anions ranging f
rom dumbbells to large three-dimensional structures. Z(SiSi) in Li57Si
43 is not strongly temperature dependent and consequently the poly-ani
ons are fairly stable. Covalently bonded Si is absent in liquid Li80Si
20. The RMC modelling indicates that individual Si atoms are well sepa
rated. This suggests that the covalent character of Si in the Si-rich
alloys (Li65Si35 and Li57Si43) changes to a more ionic character in Li
80Si20.