Dispersion-corrected Atom-centered Potentials Research Articles

Assessing the Performances of Dispersion-Corrected Density Functional Methods for Predicting the Crystallographic Properties of High Nitrogen Energetic Salts.

Several density functional methods with corrections for long-range dispersion interactions are evaluated for their capabilities to describe the crystallographic lattice properties of a set of 26 high nitrogen-content salts relevant for energetic materials applications. Computations were done using methods that ranged from adding atom-atom dispersion corrections with environment-independent and environment-dependent coefficients, to methods that incorporate dispersion effects via dispersion-corrected atom-centered potentials (DCACP), to methods that include nonlocal corrections. Among the functionals tested, the most successful is the nonlocal optPBE-vdW functional of Klimeš and Michaelides that predicts unit cell volumes for all crystals of the reference set within the target error range of ±3% and gives individual lattice parameters with a mean average percent error of less than 0.81%. The DCACP, Grimme's D3, and Becke and Johnson's exchange-hole (XDM) methods, when used with the BLYP, PBE, and B86b functionals, respectively, are also quite successful at predicting the lattice parameters of the test set.

Structure and Dynamics of Liquid Water from ab Initio Molecular Dynamics-Comparison of BLYP, PBE, and revPBE Density Functionals with and without van der Waals Corrections.

We investigate the accuracy provided by different treatments of the exchange and correlation effects, in particular the London dispersion forces, on the properties of liquid water using ab initio molecular dynamics simulations with density functional theory. The lack of London dispersion forces in generalized gradient approximations (GGAs) is remedied by means of dispersion-corrected atom-centered potentials (DCACPs) or damped atom-pairwise dispersion corrections of the C6R(-6) form. We compare results from simulations using GGA density functionals (BLYP, PBE, and revPBE) with data from their van der Waals (vdW) corrected counterparts. As pointed out previously, all vdW-corrected BLYP simulations give rise to highly mobile water whose softened structure is closer to experimental data than the one predicted by the bare BLYP functional. Including vdW interactions in the PBE functional, on the other hand, has little influence on both structural and dynamical properties of water. Augmenting the revPBE functional with either damped atom-pairwise dispersion corrections or DCACP evokes opposite behaviors. The former further softens the already under-structured revPBE water, whereas the latter makes it more glassy. These results demonstrate the delicacy needed in describing weak interactions in molecular liquids.

Dispersion Corrected Atom-Centered Potentials for Phosphorus.

Dispersion-corrected atom-centered potentials (DCACPs) for the element phosphorus were generated and tested for the BLYP, BP, and PBE generalized gradient approximations of the exchange-correlation functional. The accuracy and transferability of the DCACPs were tested by evaluating the interaction energy of different weakly bound molecular systems (P2, PH3, and PN dimers). These results were compared to reference CCSD(T) calculations and standard density functional theory (DFT). The DCACP were also tested in the case of condensed phase systems. Specifically, the density and cohesive energies of β-white and black phosphorus were estimated and compared to available experimental data. Our results show an overall strong improvement both at the qualitative and quantitative level, with respect to uncorrected generalized gradient approximation DFT results for all three functionals. In particular, BLYP-corrected results show the maximal transferability, reporting for all systems a deviation from CCSD(T) results of less than 1% in the predicted binding energies.

Hydrogen Bonding Described Using Dispersion-Corrected Density Functional Theory

In recent works, dispersion-corrected atom-centered potentials (DCACPs) were developed as a method to account for long-range dispersion forces between molecules in density functional theory calculations within the generalized gradient approximation (GGA). Here, we test the ability of DCACPs to improve the GGA treatment of hydrogen-bonded systems. We assessed both BLYP and dispersion-corrected BLYP with respect to benchmark calculations for the hydrogen bond lengths and binding energies of 20 complexes containing the elements C, H, N, O, and S. Benchmark data included geometries calculated using MP2 and CCSD(T) and binding energies using W2, W1, CBS-QB3, and other CCSD(T) extrapolation schemes. With respect to benchmark methods, dispersion-corrected BLYP exhibited a mean signed error of 0.010 A in the hydrogen bond length and a mean relative error of 5.1% in the hydrogen bond binding energy. By comparison, uncorrected BLYP exhibited error statistics of 0.036 A and 15.9%, respectively. We conclude that DCACPs robustly improve the BLYP description of hydrogen-bonded systems at small additional computational cost. New benchmark geometries (MP2/aug-cc-pVTZ) and new benchmark binding energies (W1) are presented for seven complexes, and the remaining benchmark data were taken from previous literature.

Importance of van der Waals Interactions in Liquid Water

We present ab initio molecular dynamics studies on liquid water using density functional theory in conjunction with either dispersion-corrected atom-centered potentials or empirical van der Waals corrections. Our results show that improving the description of van der Waals interactions in DFT-GGA leads to a softening of liquid water's structure with higher mobility. The results obtained with dispersion-corrected atom-centered potentials are especially encouraging. In particular, the radial distribution functions are in better agreement with experiment, and the self-diffusion coefficient increases by more than three-fold compared with the one predicted by the BLYP functional. This work demonstrates that van der Waals interactions are essential in fine-tuning both structural and dynamical properties of liquid water.

Accurate DFT Descriptions for Weak Interactions of Molecules Containing Sulfur.

Dispersion corrected atom centered potentials (DCACPs) have been shown to significantly improve the density functional theory (DFT) description of weak interactions. In this work, we have calibrated a DCACP for sulfur in combination with the widely used Generalized Gradient Approximation (GGA) BLYP, thereby augmenting the existing library of DCACPs for the first- and second-row elements H, C, N, O, and rare gases. Three weakly bound complexes as well as elemental (orthorhombic) sulfur are used as test cases to evaluate the transferability of the DCACP to different chemical environments. It is found that the sulfur DCACP systematically improves the agreement of DFT-calculated weak interactions with respect to MP2 and CCSD(T) level results.

Atom-Centered Potentials to Describe Dispersion Forces in Density Functional Theory

London dispersion forces are of primordial importance in chemical and biological systems. The Kohn–Sham formalism of density functional theory combined with many popular approximated exchange-correlation functionals either provides sporadic results or fails completely to account for these forces. Dispersion-corrected atom-centered potentials mimic the effect of these forces via atomic orbital-dependent nonlocal potentials whose parameters are obtained by calibrating against references of chosen accuracy. This scheme has shown encouraging outcomes despite its empiricism; the aim of this communication is to give a brief review on the development and applications to date of this promising approach.

Predicting Noncovalent Interactions between Aromatic Biomolecules with London-Dispersion-Corrected DFT

Within the framework of Kohn-Sham density functional theory, interaction energies of hydrogen bonded and pi-pi stacked supramolecular complexes of aromatic heterocycles, nucleobase pairs, and complexes of nucleobases with the anti-cancer agent ellipticine as well as its derivatives are evaluated. Dispersion-corrected atom-centered potentials (DCACPs) are employed together with a generalized gradient approximation to the exchange correlation functional. For all systems presented, the DCACP calculations are in very good agreement with available post Hartree-Fock quantum chemical results. Estimates of 3-body contributions (<15% of the respective interaction energy) and deformation energies (5-15% of the interaction energy) are given. Based on our results, we predict a strongly bound interaction energy profile for the ellipticine intercalation process with a stabilization of nearly 40 kcal/mol (deformation energy not taken into account) when fully intercalated. The frontier orbitals of the intercalator-nucleobase complex and the corresponding non-intercalated nucleobases are investigated and show significant changes upon intercalation. The results not only offer some insights into the systems investigated but also suggest that DCACPs can serve as an effective way to achieve higher accuracy in density functional theory without incurring an unaffordable computational overhead, paving ways for more realistic studies on biomolecular complexes in the condensed phase.

Weakly Bonded Complexes of Aliphatic and Aromatic Carbon Compounds Described with Dispersion Corrected Density Functional Theory.

Interaction energies and structural properties of van der Waals complexes of aliphatic hydrocarbons molecules and crystals of aromatic hydrocarbon compounds are studied using density functional theory augmented with dispersion corrected atom centered potentials (DCACPs). We compare the performance of two sets of DCACPs, (a) DCACP-MP2, a correction for carbon only, generated using MP2 reference data and a penalty functional that includes only equilibrium properties and (b) DCACP-CCSD(T), a set that has been calibrated against CCSD(T) reference data using a more elaborate penalty functional that explicitly takes into account some long-range properties and uses DCACP corrections for hydrogen and carbon atoms. The agreement between our results and high level ab initio or experimental data illustrates the transferability of the DCACP scheme for the gas and condensed phase as well as for different hybridization states of carbon. The typical error of binding energies for gas-phase dimers amounts to 0.3 kcal/mol. This work demonstrates that only one DCACP per element is sufficient to correct for weak interactions in a large variety of systems, irrespective of the hybridization state.

Library of dispersion-corrected atom-centered potentials for generalized gradient approximation functionals: Elements H, C, N, O, He, Ne, Ar, and Kr

Parameters for analytical dispersion-corrected atom-centered potentials (DCACPs) are presented to improve the description of London dispersion forces within the generalized gradient approximation functionals BLYP, BP, and PBE. A library of DCACPs for hydrogen, carbon, nitrogen, oxygen, helium, neon, argon, and krypton was obtained by calibrating against high-level CCSD(T) or configuration interaction references. The performance and transferability of DCACPs were tested on weakly bound complexes and provide excellent results throughout all investigated systems.