Kohn–Sham density functionals are widely used; however, no currently available exchange–correlation functional can predict all chemical properties with chemical accuracy. Here we report a new functional, called MN15, that has broader accuracy than any previously available one. The properties considered in the parameterization include bond energies, atomization energies, ionization potentials, electron affinities, proton affinities, reaction barrier heights, noncovalent interactions, hydrocarbon thermochemistry, isomerization energies, electronic excitation energies, absolute atomic energies, and molecular structures. When compared with 82 other density functionals that have been defined in the literature, MN15 gives the second smallest mean unsigned error (MUE) for 54 data on inherently multiconfigurational systems, the smallest MUE for 313 single-reference chemical data, and the smallest MUE on 87 noncovalent data, with MUEs for these three categories of 4.75, 1.85, and 0.25 kcal mol⁻¹, respectively, as compared to the average MUEs of the other 82 functionals of 14.0, 4.63, and 1.98 kcal mol⁻¹. The MUE for 17 absolute atomic energies is 7.4 kcal mol⁻¹ as compared to an average MUE of the other 82 functionals of 34.6 kcal mol⁻¹. We further tested MN15 for 10 transition-metal coordination energies, the entire S66x8 database of noncovalent interactions, 21 transition-metal reaction barrier heights, 69 electronic excitation energies of organic molecules, 31 semiconductor band gaps, seven transition-metal dimer bond lengths, and 193 bond lengths of 47 organic molecules. The MN15 functional not only performs very well for our training set, which has 481 pieces of data, but also performs very well for our test set, which has 823 data that are not in our training set. The test set includes both ground-state properties and molecular excitation energies. For the latter MN15 achieves simultaneous accuracy for both valence and Rydberg electronic excitations when used with linear-response time-dependent density functional theory, with an MUE of less than 0.3 eV for both types of excitations.

Significance: Kohn–Sham density functional theory (KS-DFT) has been widely utilized for applications in chemistry, condensed-matter physics, and materials science, but the accuracy of KS-DFT depends on the approximations to the exchange–correlation functional, and thus functional development is very important. The M06 and M06-2X functionals, which are hybrid metafunctionals, have been widely used due to their broad applicability. In this study, we present a hybrid metafunctional called revM06 that has broader accuracy than either M06 or M06-2X. As a result, the revM06 functional is well suited for a broad range of applications on main-group chemistry, transition-metal chemistry, and molecular structure prediction. The reoptimization takes advantage of the better databases and of our recently developed strategy for obtaining smoother functionals.

Significance: Local exchange−correlation functionals, which depend on the local spin densities, their gradients, and the local spin-specific kinetic energy densities, have been widely used for electronic structure calculations in both chemistry and physics, owing to their computational efficiency in plane wave codes and for large molecules and to their relatively high accuracy for transition metals and other inherently multiconfigurational systems. Minnesota 2006 local functional (M06-L) has proven to be one of the most accurate local functionals currently available, but it has room for improvement with regard to numerical stability and overall accuracy. Here we present a revised M06-L functional, named revM06-L, which gives both smoother potential energy curves and improved overall accuracy, especially for chemical reaction barrier heights, noncovalent interactions, and solid-state physics.

An accurate and efficient ab initio molecular dynamics (AIMD) simulation of liquid water was made possible using the fragment-based approach (J. F. Liu, X. He and J. Z. H. Zhang, Phys. Chem. Chem. Phys., 2017, 19, 11931–11936). In this study, we advance the AIMD simulations using the fragment-based coupled cluster (CC) theory, more accurately revealing the structural and dynamical properties of liquid water under ambient conditions. The results show that the double-donor hydrogen-bond configurations in liquid water are nearly in balance with the single-donor configurations, with a slight bias towards the former. Our observation is in contrast to the traditional tetrahedral water structure. The hydrogen-bond switching dynamics in liquid water are very fast, with a hydrogen-bond life time of around 0.78 picoseconds, determined using AIMD simulation at the CCD/aug-cc-pVDZ level. This time scale is remarkably shorter than the ∼3.0 picoseconds that is commonly obtained from traditional nonpolarized force fields and density functional theory (DFT) based first-principles simulations. Additionally, the obtained radial distribution functions, triplet oxygen angular distribution, diffusion coefficient, and the dipole moment of the water molecule are uniformly in good agreement with the experimental observations. The current high-level AIMD simulation sheds light on the understanding of the structural and dynamical properties of liquid water.