Hydrogen/silicon complexes in silicon from computational searches

Morris, Andrew J.; Pickard, Chris J.; Needs, R. J.

doi:10.1103/physrevb.78.184102

Cited by 48 publications

(49 citation statements)

References 37 publications

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“…We have used AIRSS to study defect complexes in Si consisting of combinations of H, N, and O impurity atoms and Si self-interstitials and vacancies [97,98]. Most of the searches were performed with 32-atom supercells, although we used larger cells for a few searches.…”

Section: Defects In Siliconmentioning

confidence: 99%

Ab initiorandom structure searching

Pickard

Needs²

2011

J. Phys.: Condens. Matter

1,116

989

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Abstract. It is essential to know the arrangement of the atoms in a material in order to compute and understand its properties. Searching for stable structures of materials using first-principles electronic structure methods, such as density functional theory (DFT), is a rapidly growing field. Here we describe our simple, elegant and powerful approach to searching for structures with DFT which we call ab initio random structure searching (AIRSS). Applications to discovering structures of solids, point defects, surfaces, and clusters are reviewed. New results for iron clusters on graphene, silicon clusters, polymeric nitrogen, hydrogen-rich lithium hydrides, and boron are presented.

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Section: Defects In Siliconmentioning

confidence: 99%

Ab initiorandom structure searching

Pickard

Needs²

2011

J. Phys.: Condens. Matter

1,116

989

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“…34,35 More recently is has also been applied to the Li-P system 36 and defects in technologically relevant ceramics, 37,38 semiconductors 39,40 and LIBs. 41,42 Since in an AIRSS calculation each random starting configuration is independent from another, the search algorithm is trivially parallelisable, making high-throughput computation straightforward.…”

Section: Methodsmentioning

confidence: 99%

Thermodynamically stable lithium silicides and germanides from density functional theory calculations

Morris¹,

Grey²,

Pickard³

2014

Phys. Rev. B

Self Cite

113

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High-throughput density-functional-theory (DFT) calculations have been performed on the Li-Si and Li-Ge systems. Lithiated Si and Ge, including their metastable phases, play an important technological rôle as Liion battery (LIB) anodes. The calculations comprise structural optimisations on crystal structures obtained by swapping atomic species to Li-Si and Li-Ge from the X-Y structures in the International Crystal Structure Database, where X={Li,Na,K,Rb,Cs} and Y={Si,Ge,Sn,Pb}. To complement this at various Li-Si and Li-Ge stoichiometries, ab initio random structure searching (AIRSS) was also performed. Between the ground-state stoichiometries, including the recently found Li 17 Si 4 phase, the average voltages were calculated, indicating that germanium may be a safer alternative to silicon anodes in LIB, due to its higher lithium insertion voltage. Calculations predict high-density Li 1 Si 1 and Li 1 Ge 1 P4/mmm layered phases which become the ground state above 2.5 and 5 GPa respectively and reveal silicon and germanium's propensity to form dumbbells in the Li x Si, x = 2.33 − 3.25 stoichiometry range. DFT predicts the stability of the Li 11 Ge 6 Cmmm, Li 12 Ge 7 Pnma and Li 7 Ge 3 P32 1 2 phases and several new Li-Ge compounds, with stoichiometries

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“…Ab initio random structure searching (AIRSS) 16 has been successful in predicting the ground-state structures of point defects (including the interaction of impurities with vacancies) in semiconductors 17,18 and ceramics. 19,20 The initial structures for the searches were prepared as follows.…”

Section: })mentioning

confidence: 99%

Lithiation of silicon via lithium Zintl-defect complexes from first principles

et al. 2013

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An extensive search for low-energy lithium defects in crystalline silicon using density-functional-theory methods and the ab initio random structure searching (AIRSS) method shows that the four-lithium-atom substitutional point defect is exceptionally stable. This defect consists of four lithium atoms with strong ionic bonds to the four under-coordinated atoms of a silicon vacancy defect, similar to the bonding of metal ions in Zintl phases. This complex is stable over a range of silicon environments, indicating that it may aid amorphization of crystalline silicon and form upon delithiation of the silicon anode of a Li-ion rechargeable battery. }).For example, the lithium substitutional defect is denoted by {Li,V } since it comprises a lithium atom within a silicon vacancy. A lithium-vacancy complex was assigned to an electron paramagnetic resonance (EPR) center by Goldstein 2 and lithium drift rate experiments have also shown that lithium binds to vacancies, preventing further mobility.3 Our density-functional-theory (DFT) calculations show that the formation of a Frenkel-type impurity defect ({Li,V ,I }) from a T d interstitial Li atom requires an energy of 3.73 eV, which is in excellent agreement with the value of 3.75 eV calculated by Wan et al. 4 Wan et al. suggested that the substitutional lithium defect, {Li,V } will not form due to its large formation energy. However, we calculate its formation energy from bulk silicon and lithium metal to be 3.09 eV, and hence {Li,V } is more stable than a separated vacancy and lithium interstitial ({V } and {Li}). It is likely that silicon vacancies play a significant role in the interaction between lithium and silicon.Along with the wide range of technological uses of silicon, such as semiconductor devices and photovoltaics, it has recently been proposed as an anode for lithium-ion batteries. Lithium intercalated graphite is the standard lithium-ion battery (LIB) negative electrode material, due to its good rate capability and cyclability, but demand for even higher performance LIBs has motivated the investigation of other materials. Silicon is an attractive alternative since it has 10 times the gravimetric and volumetric capacity of graphite (calculated from the initial mass and volume of silicon) but, unlike graphite, silicon undergoes structural changes on lithiation. 5-7In the first stages of lithiation, in which silicon atoms greatly outnumber lithium, it has been proposed that lithiation occurs as interstitial lithium defects form near the silicon surface. 8 Previous theoretical studies have shown that a single lithium atom in bulk silicon resides at the T d site and that at higher concentrations lithium clusters can promote the breaking of silicon-silicon bonds. 4,9,10 There are equal numbers of T d sites and silicon atoms in c-Si and, since a-Li y Si forms at y ≈ 0.3 in micron-sized silicon clusters (a Li:Si ratio of ≈ 1 : 3 11,12 ), the presence of lithium must lead to the breaking of silicon-silicon bonds before all T d sites are filled with lithium. Chan e...

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Hydrogen/silicon complexes in silicon from computational searches

Cited by 48 publications

References 37 publications

Ab initiorandom structure searching

Ab initiorandom structure searching

Thermodynamically stable lithium silicides and germanides from density functional theory calculations

Lithiation of silicon via lithium Zintl-defect complexes from first principles

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