Computationally-efficient semilocal approximations of density functional theory at the level of the local spin density approximation (LSDA) or generalized gradient approximation (GGA) poorly describe weak interactions. We show improved descriptions for weak bonds (without loss of accuracy for strong ones) from a newly-developed semilocal meta-GGA (MGGA), by applying it to molecules, surfaces, and solids. We argue that this improvement comes from using the right MGGA dimensionless ingredient to recognize all types of orbital overlap.PACS numbers: 34.20.Gj, 31.15.E-, 87.15.ADue to its computational efficiency and reasonable accuracy, the Kohn-Sham density functional theory [1][2][3] with semilocal approximations to the exchangecorrelation energy, e.g., the local spin density approximation (LSDA) [4,5] and the standard Perdew-BurkeErnzerhof (PBE) generalized gradient approximation (GGA) [6], is one of the most widely-used electronic structure methods in materials science, surface science, condensed matter physics, and chemistry. Semilocal approximations display a well-understood error cancellation between exchange and correlation in bonding regions. Thus some intermediate-range correlation effects, important for strong and weak bonds, are carried by the exchange part of the approximation. However, it is well-known that these approximations cannot yield correct long-range asymptotic dispersion forces [7]. This raises doubts about the suitability of semilocal approximations for the description of weak interactions (including hydrogen bonds and van der Waals interactions), even near equilibrium where most interesting properties occur. These doubts are supported by the performance of LSDA and GGAs, which are not very useful for many important systems and properties (such as DNA, physisorption on surfaces, most biochemistry, etc.).However, these doubts are challenged by recent developments in semilocal meta-GGAs (MGGA) [8][9][10][11][12][13][14] (which are useful by themselves and as ingredients of hybrid functionals [14]). Compared to GGAs, which use the density n(r) and its gradient ∇n as inputs, MGGAs additionally include the positive kinetic energy density τ = k |∇ψ k | 2 /2 of the occupied orbitals ψ k . For simplicity, we suppress the spin here. By including training sets of noncovalent interactions, the moleculeoriented and heavily-parameterized M06L MGGA was trained to capture medium-range exchange and correlation energies that dominate equilibrium structures of noncovalent complexes [9]. Madsen et al. showed that the inclusion of the kinetic energy densities enables MGGAs to discriminate between dispersive and covalent interactions, which makes the M06L MGGA [9] suitable for layered materials bonded by van der Waals interactions [15,16]. Besides improvement for noncovalent bonds, simultaneous improvement for metallic and covalent bonds is also an outstanding problem for semilocal functionals [17,18]. Ref. 18 has shown that the revised Tao-Perdew-Staroverov-Scuseria (revTPSS) [10] MGGA, due to the inclusion of ...

This bibliometric study of a large publication set dealing with research on climate change aims at mapping the relevant literature from a bibliometric perspective and presents a multitude of quantitative data: (1) The growth of the overall publication output as well as (2) of some major subfields, (3) the contributing journals and countries as well as their citation impact, and (4) a title word analysis aiming to illustrate the time evolution and relative importance of specific research topics. The study is based on 222,060 papers (articles and reviews only) published between 1980 and 2014. The total number of papers shows a strong increase with a doubling every 5–6 years. Continental biomass related research is the major subfield, closely followed by climate modeling. Research dealing with adaptation, mitigation, risks, and vulnerability of global warming is comparatively small, but their share of papers increased exponentially since 2005. Research on vulnerability and on adaptation published the largest proportion of very important papers (in terms of citation impact). Climate change research has become an issue also for disciplines beyond the natural sciences. The categories Engineering and Social Sciences show the strongest field-specific relative increase. The Journal of Geophysical Research, the Journal of Climate, the Geophysical Research Letters, and Climatic Change appear at the top positions in terms of the total number of papers published. Research on climate change is quantitatively dominated by the USA, followed by the UK, Germany, and Canada. The citation-based indicators exhibit consistently that the UK has produced the largest proportion of high impact papers compared to the other countries (having published more than 10,000 papers). Also, Switzerland, Denmark and also The Netherlands (with a publication output between around 3,000 and 6,000 papers) perform top—the impact of their contributions is on a high level. The title word analysis shows that the term climate change comes forward with time. Furthermore, the term impact arises and points to research dealing with the various effects of climate change. The discussion of the question of human induced climate change towards a clear fact (for the majority of the scientific community) stimulated research on future pathways for adaptation and mitigation. Finally, the term model and related terms prominently appear independent of time, indicating the high relevance of climate modeling.

We present a global hybrid meta-generalized gradient approximation (meta-GGA) with three empirical parameters, as well as its underlying semilocal meta-GGA and a meta-GGA with only one empirical parameter. All of them are based on the new meta-GGA resulting from the understanding of kinetic-energy-density dependence [J. Chem. Phys. 137, 051101 (2012)]. The obtained functionals show robust performances on the considered molecular systems for the properties of heats of formation, barrier heights, and noncovalent interactions. The pair-wise additive dispersion corrections to the functionals are also presented.

Growth of science is a prevalent issue in science of science studies. In recent years, two new bibliographic databases have been introduced, which can be used to study growth processes in science from centuries back: Dimensions from Digital Science and Microsoft Academic. In this study, we used publication data from these new databases and added publication data from two established databases (Web of Science from Clarivate Analytics and Scopus from Elsevier) to investigate scientific growth processes from the beginning of the modern science system until today. We estimated regression models that included simultaneously the publication counts from the four databases. The results of the unrestricted growth of science calculations show that the overall growth rate amounts to 4.10% with a doubling time of 17.3 years. As the comparison of various segmented regression models in the current study revealed, models with four or five segments fit the publication data best. We demonstrated that these segments with different growth rates can be interpreted very well, since they are related to either phases of economic (e.g., industrialization) and/or political developments (e.g., Second World War). In this study, we additionally analyzed scientific growth in two broad fields (Physical and Technical Sciences as well as Life Sciences) and the relationship of scientific and economic growth in UK. The comparison between the two fields revealed only slight differences. The comparison of the British economic and scientific growth rates showed that the economic growth rate is slightly lower than the scientific growth rate.

Errors for systems with noninteger occupation have been connected to common failures of density functionals. Previously, global hybrids and pure density functionals have been investigated for systems with noninteger charge and noninteger spin state. Local hybrids have not been investigated for either of those systems to the best of our knowledge. This study intends to close this gap. We investigate systems with noninteger charge to assess the many-electron self-interaction error and systems with noninteger spin state to assess the spin polarization error of recently proposed local hybrids and their range-separated variants. We find that long-range correction is very important to correct for many-electron self-interaction error in cations, whereas most full-range local hybrids seem to be sufficient for anions, where long-range-corrected density functionals tend to overcorrect. On the other hand, while all hitherto proposed long-range-corrected density functionals show large spin polarization errors, the Perdew-Staroverov-Tao-Scuseria (PSTS) functional performs best of all local hybrids in this case and shows an outstanding behavior for the dependence of the energy on the spin polarization.