On the elastic properties of lithium, sodium and potassium oxide. An ab initio study

Dovesi, Roberto; Roetti, C.; Freyria-Fava, C.; Prencipe, Mauro; Saunders, V. R.

doi:10.1016/0301-0104(91)87032-q

Cited by 256 publications

(187 citation statements)

References 25 publications

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“…Alkali metal oxides K 2 O, Na 2 O and Rb 2 O also have the antifluorite structure at ambient conditions [26,27]. The only alkali metal oxide exception is Cs 2 O, which has been seen to possess the CdCl 2 structure [28] which, however, is a simple rhombohedral distortion of the fluorite structure.…”

Section: Discussionmentioning

confidence: 99%

Pressure-induced antifluorite-to-anticotunnite phase transition in lithium oxide

et al. 2006

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Using synchrotron angle-dispersive x-ray diffraction (ADXD) and Raman spectroscopy on samples of Li 2 O pressurized in a diamond anvil cell, we observed a reversible phase change from the cubic antifluorite (α, Fm-3m) to orthorhombic anticotunnite (β, Pnma) phase at 50(±5) GPa at ambient temperature. This transition is accompanied by a relatively large volume collapse of 5.4 (±0.8) % and large hysteresis upon pressure reversal (P down at ∼25 GPa). Contrary to a recent study, our data suggest that the high-pressure β-phase (B o = 188±12 GPa) is substantially stiffer than the low-pressure α-phase (B o = 90±1 GPa). A relatively strong and pressure-dependent preferred orientation in β-Li 2 O is observed. The present result is in accordance with the systematic behavior of antifluorite-to-anticotunnite phase transitions occurring in the alkali-metal sulfides.

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Section: Discussionmentioning

confidence: 99%

Pressure-induced antifluorite-to-anticotunnite phase transition in lithium oxide

et al. 2006

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“…В вычислениях использовались ба-зисные наборы линейных комбинаций атомных орбита-лей [39][40][41][42][43][44] и градиентный функционал PBE-GGA [37].…”

Section: метод расчетаunclassified

Влияние давления на структуру и электронные свойства LiClO-=SUB=-4-=/SUB=-, NaClO-=SUB=-4-=/SUB=-, KClO-=SUB=-4-=/SUB=-, NH-=SUB=-4-=/SUB=-ClO-=SUB=-4-=/SUB=-

Korabel’nikov¹,

Журавлев²

2017

Физика Твердого Тела

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Влияние давления на структурные и электронные свойства перхлоратов лития, натрия, калия и аммония исследовано в рамках теории функционала плотности с учетом дисперсионного взаимодействия Ван-дер-Ваальса. Вычислены барические зависимости геометрических параметров, ширин запрещенных зон, плотностей состояний, зарядовых распределений, атомных зарядов. Установлено, что сжимаемость перхлоратов анизотропная, что связано с различием параметров решетки и природы межатомных связей. Под давлением катион аммония поворачивается вокруг оси b на угол ∼ 9 • . Ширины запрещенных зон перхлоратов составляют ∼ 4.5−4.7 eV и с давлением увеличиваются.

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“…We used all-electron basis sets of triple-ζ quality for Na, S, and K, 47,48 but for Cu, Ga, Se, Cd, and In, we used the SBKJC Relativistic effective core potentials (based on angular momentum projection operators 49,50 ) and the associated basis sets. 51 Thus we treat explicitly just the outer 19 electrons for Cu, 21 for Ga, 6 for Se, 20 for Cd, and 21 for In.…”

Section: Computational Detailsmentioning

confidence: 99%

Predicted roles of defects on band offsets and energetics at CIGS (Cu(In,Ga)Se2/CdS) solar cell interfaces and implications for improving performance

Xiao

Goddard

2014

The Journal of Chemical Physics

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The laboratory performance of CIGS (Cu(In,Ga)Se 2 ) based solar cells (20.8% efficiency) makes them promising candidate photovoltaic devices. However, there remains little understanding of how defects at the CIGS/CdS interface affect the band offsets and interfacial energies, and hence the performance of manufactured devices. To determine these relationships, we use density functional theory with the B3PW91 hybrid functional that we validate to provide very accurate descriptions of the band gaps and band offsets. This confirms the weak dependence of band offsets on surface orientation observed experimentally. We predict that the conduction band offset (CBO) of perfect CuInSe 2 /CdS interface is large, 0.79 eV, which would dramatically degrade performance. Moreover we show that band gap widening induced by Ga adjusts only the valence band offset, and we find that Cd impurities do not significantly affect the CBO. Thus we show that Cu vacancies at the interface play the key role in enabling the tunability of CBO. We predict that Na further improves the CBO through electrostatically elevating the valence levels to decrease the CBO, explaining the observed essential role of Na for high performance. Moreover we find that K leads to a dramatic decrease in the CBO to 0.05 eV, much better than Na. We suggest that the efficiency of CIGS devices might be improved substantially by tuning the ratio of Na to K, with the improved phase stability of Na balancing phase instability from K. All these defects reduce interfacial stability slightly, but not significantly.

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On the elastic properties of lithium, sodium and potassium oxide. An ab initio study

Cited by 256 publications

References 25 publications

Pressure-induced antifluorite-to-anticotunnite phase transition in lithium oxide

Pressure-induced antifluorite-to-anticotunnite phase transition in lithium oxide

Влияние давления на структуру и электронные свойства LiClO-=SUB=-4-=/SUB=-, NaClO-=SUB=-4-=/SUB=-, KClO-=SUB=-4-=/SUB=-, NH-=SUB=-4-=/SUB=-ClO-=SUB=-4-=/SUB=-

Predicted roles of defects on band offsets and energetics at CIGS (Cu(In,Ga)Se2/CdS) solar cell interfaces and implications for improving performance

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