Browsing by Author "Smet, Jurgen H."

Now showing 1 - 3 of 3

Alkali metals inside bi-layer graphene and MoS2: Insights from first-principles calculations
(2020-09) Chepkasov, Ilya V.; Ghorbani-Asl, Mahdi; Popov, Zakhar I.; Smet, Jurgen H.; Krasheninnikov, Arkady V.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Contrary to a wide-spread belief that alkali metal (AM) atoms intercalated into layered materials form single-layer structures only, recent experiments [Nature 564 (2018) 234] showed that multi-layer configurations of lithium are possible in bi-layer graphene. Using state-of-the-art first-principles calculations, we systematically study the intercalation energetics for various AMs (Li, Na, K, Rb, Cs) in bi-layer graphene and MoS2. We demonstrate that for bi-layer graphene as host the formation energy of multi-layer structures is negative for K, Rb and Cs and only slightly positive for both Li and Na. In view of the previous experimental data on lithium, a multi-layer of Na might therefore form, while it is well-known that single-layers of Na in graphitic hosts are energetically very unfavorable. In MoS2, multi-layer structures are considerably higher in energy than the single-layer ones, but the formation of the former can still occur, especially for the AMs with the lowest electro-negativity. To rationalize the results, we assess the charge transfer from the intercalants to the host material and analyze the interplay between the ionic and covalent bonding of AM and host atoms. While our theoretical effort primarily focuses on the fundamental aspects of AM intercalation, our findings may stimulate experimental work addressing multi-layer intercalation to maximize the capacity of anode materials in AM ion batteries.
Single- and Multilayers of Alkali Metal Atoms inside Graphene/MoS2Heterostructures: A Systematic First-Principles Study
(2022-09-07) Chepkasov, Ilya V.; Smet, Jurgen H.; Krasheninnikov, Arkady V.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Stacking various 2D materials in van der Waals heterostructures is a novel approach to design new systems, which can host alkali metal (AM) atoms to tune their electronic properties or store energy. Using state-of-the-art first-principles calculations, we systematically study the intercalation of the most widespread AMs (Li, Na, and K) into a graphene/MoS2 heterostructure. Contrary to the previous work on the intercalation of AMs into various heterostructures based on 2D materials, we consider not only single-, but also multi-layer configurations of AM atoms. We assess the intercalation energetics for various concentrations of AM atoms, calculate charge transfer from AM atoms to the host system, and show that although intercalation of AMs as a single layer is energetically preferable, multi-layer configurations can exist at high concentrations of AM atoms. We further demonstrate that the transition of the MoS2 layer from the H to T′ phase is possible upon Li intercalation, but not for Na or K. Our findings should help to better understand the behavior of heterostructures upon AM atom intercalation and may stimulate further experiments aimed at the tailoring of heterostructure properties and increasing the capacity of anode materials in AM ion batteries.
Vibrational Properties of a Two-Dimensional Silica Kagome Lattice
(2016-12-27) Björkman, Torbjörn; Skakalova, Viera; Kurasch, Simon; Kaiser, Ute; Meyer, Jannik C.; Smet, Jurgen H.; Krasheninnikov, Arkady V.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Kagome lattices are structures possessing fascinating magnetic and vibrational properties, but in spite of a large body of theoretical work, experimental realizations and investigations of their dynamics are scarce. Using a combination of Raman spectroscopy and density functional theory calculations, we study the vibrational properties of two-dimensional silica (2D-SiO2), which has a kagome lattice structure. We identify the signatures of crystalline and amorphous 2D-SiO2 structures in Raman spectra and show that, at finite temperatures, the stability of 2D-SiO2 lattice is strongly influenced by phonon-phonon interaction. Our results not only provide insights into the vibrational properties of 2D-SiO2 and kagome lattices in general but also suggest a quick nondestructive method to detect 2D-SiO2.