Waals Inclusive Density Functional Theory Research Articles

Assessment of van der Waals inclusive density functional theory methods for adsorption and selective dehydrogenation of formic acid on Pt(111) surface.

In this work, we studied the adsorption and catalytic dehydrogenation of formic acid (HCOOH) on Pt(111) surface using different van der Waals inclusive density functional theory (DFT) methods. Our results indicate that the PBE + dDsC method has the best overall performance on the description of adsorption and catalytic selectivity. We found the improved van der Waals (vdW) corrected methods (PBE + D3, PBE + TS, PBE + TS-SCS, PBE + TS/IH, PBE + MBD@rsSCS, and PBE + dDsC) and optimized vdW functionals (optPBE-vdW, optB88-vdW, and optB86b-vdW) perform well to estimate the adsorption energies of HCOOH and HCOO molecules on Pt(111) surface. The vdW-inclusive DFT approaches as well as the conventional PBE functional predict a higher activation barrier for C-H breaking by comparison of O-H breaking in the selective dehydrogenation of formic acid. However, the optimized vdW functionals evidently underestimate the rate constant of C-H breaking reaction, and then fail to describe the catalytic selectivity of the HCOOH's dehydrogenation. Both PBE + dDsC and PBE predict a similar temperature dependence of the ratio of reaction rate constants for O-H breaking versus C-H breaking, though PBE functional underestimate the adsorption energies.

A van der Waals Inclusive Density Functional Theory Study of the Nature of Bonding for Thiophene Adsorption on Ni(100) and Cu(100) Surfaces

We report the results of the first-principles density functional theory calculations for the adsorption of thiophene (C4H4S) on Cu(100) and Ni(100) surfaces. The adsorption properties on these surfaces are evaluated for several adsorption configurations, and the calculations are performed with the inclusion of van der Waals (vdW) interactions invoking the optimized vdW (optB86b-vdW, optB88-vdW, and optPBE-vdW) as well as revPBE-vdW and rPW86-vdW2 functionals. In agreement with the earlier reports, on both surfaces, the most stable adsorption configurations correspond to the hollow-45 at which the thiophene adsorbs parallel to the surface. For the adsorption on Ni(100), in agreement with the experimental observations, we confirm that thiophene spontaneously ruptures via breaking of a C–S bond when the center of the molecule is placed over a bridge site. On the basis of both the bond distribution and charge transfer analysis, we conclude that the rupturing of thiophene observed at the bridge-45 configuratio...

Molecular Seesaw: Intricate Dynamics and Versatile Chemistry of Heteroaromatics on Metal Surfaces

The design of novel elementary surface processes is important for applications in catalysis, single-molecule junctions, molecular sensors, switches, and surface-mounted molecular machines. Here we demonstrate by van der Waals inclusive density functional theory calculations that a small and relatively simple heteroaromatic compound s-triazine (C3H3N3) unexpectedly possesses five metastable states when adsorbed on the Pt(111) surface. This diversity of the adsorption states stems from an interplay between versatile molecule/surface chemical bonding and van der Waals interactions and from "softening" of the aromatic ring by nitrogen substitution, which makes folding of the aromatic ring energetically much less demanding as compared to benzene. The intricate seesaw-like surface dynamics and tunable electronic structure of s-triazine show promise for applications in molecular sensors and switches. The broad implications of our findings are demonstrated for triazine- and pyrimidine-based heteroaromatic compounds and other metal surfaces.

Assessment of van der Waals inclusive density functional theory methods for layered electroactive materials.

The discovery of computationally driven materials requires efficient and accurate methods. Density functional theory (DFT) meets these two requirements for many classes of materials. However, DFT-based methods have limitations. One significant shortcoming is the inadequate treatment of weak van der Waals (vdW) interactions, which are crucial for layered materials. Here we assess the performance of various vdW-inclusive DFT approaches for predicting the structure and voltage of layered electroactive materials for Li-ion batteries, considering a set of 20 different compounds. We find that the so-called optB86b-vdW density functional improves the agreement with the experimental data, closely followed by the latest generation of dispersion correction methods. These approaches yield average relative errors for the structural parameters smaller than 3%. The average deviations for redox potentials are below 0.15 V. Looking ahead, this study identifies accurate methods for Li-ion vdW bound systems, providing enhanced predictive power to DFT-assisted design for developing new types of electroactive materials in general.

Cooperative interplay of van der Waals forces and quantum nuclear effects on adsorption: H at graphene and at coronene.

The energetic barriers that atoms and molecules often experience when binding to surfaces are incredibly important to a myriad of chemical and physical processes. However, these barriers are difficult to describe accurately with current computer simulation approaches. Two prominent contemporary challenges faced by simulation are the role of van der Waals forces and nuclear quantum effects. Here we examine the widely studied model systems of hydrogen on graphene and coronene using a van der Waals inclusive density functional theory approach together with path integral molecular dynamics at 50 K. We find that both van der Waals and quantum nuclear effects work together in a cooperative manner to dramatically reduce the barriers for hydrogen atoms to adsorb. This suggests that the low temperature hydrogenation of graphene is easier than previously thought and in more general terms that the combined roles of van der Waals and quantum tunnelling can lead to qualitative changes in adsorption.