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@ARTICLE{Akola:14666,
author = {Akola, J. and Larrucea, J. and Jones, R. O.},
title = {{P}olymorphism in phase-change materials: melt-quenched and
as-deposited amorphous structures in ${G}e_2$ ${S}b_2$
${T}e_5$ from density functional calculations},
journal = {Physical review / B},
volume = {83},
number = {9},
issn = {1098-0121},
address = {College Park, Md.},
publisher = {APS},
reportid = {PreJuSER-14666},
pages = {094113},
year = {2011},
note = {The calculations were performed on the Jugene (IBM Blue
Gene/P) and Juropa (Intel Xeon 5570) computers in the FZ
Julich with grants from the FZJ and the John von Neumann
Institute for Computing (NIC). We thank A. Filipponi for
calculating EXAFS from our partial PDF, S. Kohara, T.
Matsunaga, and N. Yamada for discussions and support, and
the Academy of Finland for funding.},
abstract = {The as-deposited (AD) amorphous structure of the prototype
phase change material Ge2Sb2Te5 (GST-225) has been studied
by density functional calculations for a 648-atom sample
generated by computer-aided deposition at 300 K. The AD
sample differs from a melt-quenched (MQ) sample in essential
ways: (1) Ge atoms are predominantly tetrahedrally
coordinated, and (2) homopolar and Ge-Sb bonds are more
common and reduce the number of ABAB squares (A = Ge, Sb; B
= Te), the characteristic building blocks of the material.
The first observation resolves the contradiction between
measured (EXAFS) and calculated Ge-Te bond lengths, and the
latter explains the very different crystallization speeds.
Sb and Te have higher chemical coordination than suggested
by the "8-N rule" of covalent networks (N is the number of
valence electrons). The EXAFS signal calculated for AD
agrees much better with experiment than that calculated for
MQ.},
keywords = {J (WoSType)},
cin = {PGI-1},
ddc = {530},
cid = {I:(DE-Juel1)PGI-1-20110106},
pnm = {Grundlagen für zukünftige Informationstechnologien},
pid = {G:(DE-Juel1)FUEK412},
shelfmark = {Physics, Condensed Matter},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000288211300003},
doi = {10.1103/PhysRevB.83.094113},
url = {https://juser.fz-juelich.de/record/14666},
}