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The analysis of the local structure of covalent glass is one of the major challenges for analyzing the amorphous structure. Usually, people use a cutoff distance to determine the coordinated atoms and relevant structural information, such as coordination number and bond angles. Recently, the electron localization function (ELF) has been used to analyze the local structure of amorphous Ge2Sb2Te5. But how to determine the EFL threshold and cutoff distance has not been reported. Here, according to the ab-initio calculations, we systematically investigate the relationship between the bond number and the ELF threshold, and also the cutoff distance in amorphous GeTe. The reasonable value of the ELF threshold and the cutoff distance are determined according to the inflection point and slope change of the bond number with ELF value respectively. Furthermore, the minimal ELF value distributions of Ge-Ge, Ge-Te and Te-Te bonds are presented. The comparison shows that the majority of removed bonds in structural analysis are weak Ge-Te bonds due to the low localization degree of electron. In contrast, the stronger Ge-Ge bonds are almost unchanged when changing the ELF threshold value from 0.58 to 0.63 because of the high localization degree of electron. The average minimal ELF value of Ge-Te bonds in crystalline GeTe is calculated, and it is close to the ELF threshold that is determined by the inflection point. t is easy to find that the Ge-Te bonds which are removed by increasing the ELF threshold are relatively weak. Therefore, these weaker bonds should be removed in structure analysis, which also means that the ELF threshold determined by the inflection point are reasonable value. Finally, based on the EFL threshold value, the coordination number and bond angle distribution of Ge in amorphous GeTe are obtained. The analysis of the coordination number of the Ge atoms shows that as the ELF threshold increases from 0.58 to 0.63, the 5- fold Ge atoms almost disappear because they are against the (8-N) rule. Furthermore, when the ELF threshold value is 0.58, the bond angle distribution analysis of Ge atoms shows that the local structure is a configuration that is mainly defectively octahedral (3-fold Ge) and distorted tetrahedral (4-fold Ge), but it remains unchanged when the threshold value increases to 0.63. It further demonstrates that all the removed chemical bonds are weaker ones as the ELF threshold increases. This approach is useful to improve the accuracy of amorphous structure analysis by obtaining the more reasonable inter-atomic bonding information. And it should be applied to the structural analyses of other systems generally.
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Keywords:
- cutoff distance /
- electron localization function /
- coordinate number /
- bond angle distribution
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[8] Xu M, Cheng Y Q, Sheng H W, Ma E 2009 Phys. Rev. Lett. 103 195502
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[11] Ovshinsky S R 1968 Phys. Rev. Lett. 21 1450
[12] Yoon S M, Choi K J, Lee N Y, Jung S W, Lee S Y, Park Y S, Yu B G, Lee S J, Yoon S G 2008 J. Electrochem. Soc. 155 H421
[13] Wang K, Steitner C, Warnwangi D, Ziegler S, Wuttig M, Tomforde J, Bensch W 2007 Microsyst. Technol. 13 203
[14] Welnic W, Wuttig M 2008 Mater. Today 11 20
[15] Wuttig M, Yamada N 2007 Nat. Mater. 6 824
[16] Kolobov A V, Fons P, Frenkel A I, Ankudinov A L, Tominaga J, Uruga T 2004 Nat. Mater. 3 703
[17] Caravati S, Bernasconi M, Khne T D, Krack M, Parrinello M 2007 Appl. Phys. Lett. 91 171906
[18] Lee T H, Elliott S R 2011 Phys. Rev. Lett. 107 145702
[19] Zhang W, Ronneberger I, Li Y, Mazzarello R 2013 Monatsh. Chem. 145 97
[20] Kresse G, Furthmuller J 1996 Comput. Mater. Sci. 6 15
[21] Rao X, Wang R Z, Cao J X, Yan H 2015 Acta Phys. Sin. 64 107303 (in Chinese) [饶雪, 王如志, 曹觉先, 严辉 2015 物理学报 64 107303]
[22] Ernzerhof M, Scuseria G E 1999 J. Chem. Phys. 110 5029
[23] Tuckerman M, Berne B J, Martyna G J 1992 J. Chem. Phys. 97 1990
[24] Nonaka T, Ohbayashi G, Toriumi Y, Mori Y, Hashimoto H 2000 Thin Solid Films 370 258
[25] Lencer D, Salinga M, Grabowski B, Hickel T, Neugebauer J, Wuttig M 2008 Nat. Mater. 7 972
[26] Welnic W, Botti S, Reining L, Wuttig M 2007 Phys. Rev. Lett. 98 4
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[1] Zallen R 1983 The Physics of Amorphous Solids (New York: Wiley) pp10-16
[2] Ziman J M 1979 Models of Disorder: The Theoretical Physics of Homogeneously Disordered Systems (Cambridge: Cambridge University Press) pp51-56
[3] Yonezawa F, Ninomiya T 1983 Topological Disorder in Condensed Matter (Berlin: Springer) pp30-39
[4] McGreevy R L, Pusztai L 1988 Mol. Simul. 1 359
[5] Parrinello M, Rahman A 1981 J. Appl. Phys. 52 7182
[6] Akola J, Jones R O 2007 Phys. Rev. B 76 235201
[7] Xu M, Cheng Y Q, Wang L, Sheng H W, Meng Y, Yang W G, Han X D, Ma E 2012 Proc. Natl. Acad. Sci. U. S. A. 109 E1055
[8] Xu M, Cheng Y Q, Sheng H W, Ma E 2009 Phys. Rev. Lett. 103 195502
[9] Hughbanks T, Hoffmann R 1983 J. Am. Chem. Soc. 105 3528
[10] Silvi B, Savin A 1994 Nature 371 683
[11] Ovshinsky S R 1968 Phys. Rev. Lett. 21 1450
[12] Yoon S M, Choi K J, Lee N Y, Jung S W, Lee S Y, Park Y S, Yu B G, Lee S J, Yoon S G 2008 J. Electrochem. Soc. 155 H421
[13] Wang K, Steitner C, Warnwangi D, Ziegler S, Wuttig M, Tomforde J, Bensch W 2007 Microsyst. Technol. 13 203
[14] Welnic W, Wuttig M 2008 Mater. Today 11 20
[15] Wuttig M, Yamada N 2007 Nat. Mater. 6 824
[16] Kolobov A V, Fons P, Frenkel A I, Ankudinov A L, Tominaga J, Uruga T 2004 Nat. Mater. 3 703
[17] Caravati S, Bernasconi M, Khne T D, Krack M, Parrinello M 2007 Appl. Phys. Lett. 91 171906
[18] Lee T H, Elliott S R 2011 Phys. Rev. Lett. 107 145702
[19] Zhang W, Ronneberger I, Li Y, Mazzarello R 2013 Monatsh. Chem. 145 97
[20] Kresse G, Furthmuller J 1996 Comput. Mater. Sci. 6 15
[21] Rao X, Wang R Z, Cao J X, Yan H 2015 Acta Phys. Sin. 64 107303 (in Chinese) [饶雪, 王如志, 曹觉先, 严辉 2015 物理学报 64 107303]
[22] Ernzerhof M, Scuseria G E 1999 J. Chem. Phys. 110 5029
[23] Tuckerman M, Berne B J, Martyna G J 1992 J. Chem. Phys. 97 1990
[24] Nonaka T, Ohbayashi G, Toriumi Y, Mori Y, Hashimoto H 2000 Thin Solid Films 370 258
[25] Lencer D, Salinga M, Grabowski B, Hickel T, Neugebauer J, Wuttig M 2008 Nat. Mater. 7 972
[26] Welnic W, Botti S, Reining L, Wuttig M 2007 Phys. Rev. Lett. 98 4
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