ARTICLE IN PRESS
S. Yamanaka et al. / Journal of Solid State Chemistry 182 (2009) 1991–2003
2003
found in BaSi6 high pressure phase. It is also established that high
pressure and high temperature condition is favorable for the
formation of Si-rich compounds in La–Si binary system as well as
in the Ba–Si binary system.
20
15
10
5
s
p
d
total
EF
Acknowledgments
This study has also been supported by a Grant-in-Aid for
Scientific Research (Grants 19105006, 19051011, and 19014016) of
the Ministry of Education, Culture, Sports, Science, and Technol-
ogy of Japan.
Appendix A. Supplementary material
0
Supplementary data associated with this article can be found
-10
-5
0
Energy, eV
20
15
10
5
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s
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Fig. 16. DOS profiles of a-LaSi5 and LaSi10 calculated by CASTEP.
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a-LaSi5 is a superconductor with Tc ¼ 11.5 K,
while the -form is metallic but not superconducting. The
b
structure of LaSi5 is very different from LaGe5. The other Si-rich
binary phase LaSi10 is composed of La@Si18 polyhedra with beer
barrel shape, which form straight columns by stacking along the
c-axis via face sharing. One-dimensional columns of La@Si18
barrels are edge-shared, and bundled with infinite Si trigonal
bipyramid chains via corner sharing. LaSi10 shows superconduc-
tivity with Tc ¼ 6.7 K. It is interesting to note that the shape of
polyhedral unit La@Si18 has a close relation with that of Ba@Si18