Charge transfer in alkaline-earth metal graphite intercalation compounds

• Published in: Carbon (New York) 2024-11, Vol.230, p.119652, Article 119652
• Main Authors: Zinni, Justine, Camerano, Luigi, Speyer, Lucie, Cahen, Sébastien, El Hajj, Inass, Bolmont, Mickaël, Medjahdi, Ghouti, Lagrange, Philippe, Lamura, Gianrico, Profeta, Gianni, Hérold, Claire
• Format: Article
• Language: English
• Subjects: Alkaline-earth metals; Charge transfer; Chemical Sciences; Density functional theory calculations; Graphite intercalation compounds; Raman spectroscopy; X-ray diffraction
• ISSN: 0008-6223
• DOI: 10.1016/j.carbon.2024.119652

The charge transfer from a metal atom towards the carbon layers in first stage graphite intercalation compounds (GIC) is a fundamental issue to explain under which conditions superconductivity sets in and the electronic properties of such ground state. To study in detail the transfer process and its evolution as a function of the nature of the intercalated metal, and especially taking in consideration the interlayer distance, we performed detailed X-Ray Diffraction and Raman scattering measurements on very high-quality bulk intercalated CaC6, SrC6 and BaC6 samples. We combined both the experimental results with detailed density functional theory calculations to give a coherent picture in which it is possible to follow the evolution of the charge transfer to the carbon layer in full agreement with the experimental data. The full comprehension of such mechanism remains a fundamental issue to explain the variation of the superconducting ground state in first stage GIC. [Display omitted] •In-plane carbon-carbon distances increase with charge transfer.•The charge transfer to graphene planes increases from Ba to Ca.•Raman spectroscopy confirms the evolution of the charge transfer as detected by XRD.•Experimental charge transfer data are supported by DFT calculations.