Potassium intercalation in graphite: A van der Waals density-functional study

Abstract

Potassium intercalation in graphite is investigated by first-principles theory. The bonding in the potassium-graphite compound is reasonably well accounted for by traditional semilocal density functional theory (DFT) calculations. However, to investigate the intercalate formation energy from pure potassium atoms and graphite requires use of a description of the graphite interlayer binding and thus a consistent account of the nonlocal dispersive interactions. This is included seamlessly with ordinary DFT by a van der Waals density functional (vdW-DF) approach [Phys. Rev. Lett. 92, 246401 (2004)]. The use of the vdW-DF is found to stabilize the graphite crystal, with crystal parameters in fair agreement with experiments. For graphite and potassium-intercalated graphite structural parameters such as binding separation, layer binding energy, formation energy, and bulk modulus are reported. Also the adsorption and sub-surface potassium absorption energies are reported. The vdW-DF description, compared with the traditional semilocal approach, is found to weakly soften the elastic response.

Desorption of n-alkanes from graphene: a van der Waals density functional study

“…The (valence) electron density is represented on the same grid with additional grid points at half the nn distance, values obtained from interpolation of the electron density and addition of compensation charges. The choice of these relatively dense (wavefunction and electron density) grids is important for the quality of the evaluation of the nonlocal correlation contribution [25]. The Brillouin zone of the unit cell is sampled according to the Monkhorst-Pack scheme by means of a 2×2×1 k-point sampling.…”

Rings sliding on a honeycomb network: Adsorption contours, interactions, and assembly of benzene on Cu(111)

“…In the vdW-DF study of the effects of adsorbate-induced relaxations of the substrate, we follow these steps by a GGA-PBE calculation of the energy difference between S a and S b . A previous study 30 documents that a grid spacing of 0.15 Å is sufficient to achieve convergence of the vdW-DF binding energy in adsorption problems when combined with the above-mentioned scheme.…”

“…The vdW-DF method provides a transferable account of general materials and bindings, ranging, e.g., from the all-covalent C-C bonding within a graphene sheet to the interlayer dispersive bonding in graphite and graphite intercalates. 30 DFT calculations using the vdW-DF has successfully characterized the adsorption of Bz on the semimetal graphene 31 and on the semiconductors silicon 32 and MoS 2 . 21 A vdW-DF study also documents that vdW interactions ͑nonlocal correlations͒ significantly affect the anchoring of phenol on an oxide.…”

“…21,28 In many respect the present vdW-DF calculations are similar to those presented in Refs. [30][31][32][33]43, and 44. The physisorption system requires us to resolve very-small energy differences ͑e.g., the variation in adsorption energy with site͒ and to ensure accurate and well-converged evaluations of changes in the nonlocal correlation E c nl ͓n͔.…”

Role of van der Waals bonding in the layered oxideV2O5: First-principles density-functional calculations

“…The reference calculation is for a unit cell that has the c direction side length four times that of the original unit cell, periodically repeated in all directions. 30 We use the same reference unit cell for the nonlocal correlation ͑E c nl ͒ reference calculations and this imposes additional constraints on the construction of the reference unit cell, as described further below.…”