The coupling constant averaged exchange–correlation energy density

The exchange–correlation energy, central to density-functional theory, may be represented in terms of the coupling constant averaged (CCA) exchange–correlation energy density. We present an approach to calculate the CCA energy density using accurate ab initio methods and its application to simple atomic systems. This function provides a link between intrinsically non-local, many-body electronic structure methods and simple local and semi-local density-functional approximations (DFAs). The CCA energy density is resolved into separate exchange and correlation terms and the features of each compared with those of quantities commonly used to construct DFAs. In particular, the more complex structure of the correlation energy density is found to exhibit features that align well with those present in the Laplacian of the density, suggesting its role as a key variable to be used in the construction of improved semi-local correlation functionals. The accurate results presented in this work are also compared with those provided by the Laplacian-dependent Becke–Roussel model for the exchange energy

FTIR/PCA study of propanol in argon matrix: the initial stage of clustering and conformational transitions

FTIR spectra of 1-propanol in an argon matrix were studied in the range 11 to 30 K. Principal component analysis of dynamic FTIR spectra and nonlinear band shape fitting has been carried out. The peaks of monomer, open dimer, mixed propanol-water dimer and those of higher H-bond clusters have been resolved and analyzed. The attribution of certain FTIR peaks has been supported by proper density functional theory calculations. Analyzing dependences of the integral band intensities of various aggregates on temperature it has been deduced that in the initial stage of clustering monomers and dimers are the basic building blocks forming higher H-bond clusters. The peaks assigned to two conformers of monomers and mixed propanol-water dimers were investigated processing the temperature dependences of their integral intensities in Arrhenius plot. The obtained values of 0.18 kJ⋅mol⁻¹ for propanol monomer and 0.26 kJ⋅mol⁻¹ for mixed dimer are well comparable with the energy differences between the global minimum conformation of 1-propanol (Gt) and some other energetically higher structures (Tt or Tg)

Contrastive neural network reveals the structure of neuroanatomical variation within bilingualism

Bilingualism varies greatly in terms of language background, age of acquisition, and learning environment, making it complex to study the relationship between language and brain structure. Age of acquisition and linguistic proficiency are both crucial factors in language acquisition research and are closely related. To better understand the relationship between bilingualism and brain structure, we created a dataset of 2,000+ brain 3D images from bilinguals and monolinguals and trained a neural network (Contrastive Variational Autoencoder, CVAE) to distinguish bilingual-specific neuroanatomical variations from those shared by monolingual groups. The initial results reveal that the common variation (e.g. scanner and sex) in brain structure shared by two groups can be identified by CVAE. More importantly, CVAE disentangled linguistic proficiency from the common variation but not age of acquisition. It suggests that compared to age of acquisition, linguistic proficiency is more correlated with brain’s structure

Fluorescence and phosphorescence of acetone in neat liquid and aqueous solution as studied by QM/MM and PCM approaches,

Electronic singlet and triplet nπ∗ absorption and emission energies of acetone in vacuum, neat liquid and aqueous solution have been calculated. Electronic states of acetone in solution have been modelled using combined molecular dynamics-quantum mechanics/molecular mechanics techniques and the polarizable continuum model. In addition, we have compared density functional theory based results to corresponding coupled cluster singles and doubles predictions. Theoretical results have also been compared to experimental data. In general, we have obtained a good description of solvent effects on the absorption energies. However, modelling of excited states explicitly is still a challenge for the applied approaches, as the solvent shifts of the singlet nπ∗ emission have been considerably underestimated and also the solvent shift related to the Stokes shifts of fluorescence was predicted to have incorrect sign compared to available experimental data

A quantum mechanics/molecular dynamics study of electric field gradient fluctuations in the liquid phase. The case of Na+ in aqueous solution

The 23Na quadrupolar coupling constant of the Na+ ion in aqueous solution has been predicted using molecular dynamics simulations and hybrid quantum mechanics/molecular mechanics methods for the calculation of electric field gradients. The developed computational approach is generally expected to provide reliable estimates of the quadrupolar coupling constants of monoatomic species in condensed phases, and we show here that intermolecular polarization and non-electrostatic interactions are of crucial importance as they result in a 100% increased quadrupolar coupling constant of the ion as compared to a simpler pure electrostatic picture. These findings question the reliability of the commonly applied classical Sternheimer approximation for the calculations of the electric field gradient. As it can be expected from symmetry considerations, the quadrupolar coupling constants of the 5- and 6-coordinated Na+ ions in solution are found to differ significantly

On the performance of quantum chemical methods to predict solvatochromic effects: The case of acrolein in aqueous solution.

The performance of the Hartree-Fock method and the three density functionals B3LYP, PBE0, and CAM-B3LYP is compared to results based on the coupled cluster singles and doubles model in predictions of the solvatochromic effects on the vertical n-->pi(*) and pi-->pi(*) electronic excitation energies of acrolein. All electronic structure methods employed the same solvent model, which is based on the combined quantum mechanics/molecular mechanics approach together with a dynamical averaging scheme. In addition to the predicted solvatochromic effects, we have also performed spectroscopic UV measurements of acrolein in vapor phase and aqueous solution. The gas-to-aqueous solution shift of the n-->pi(*) excitation energy is well reproduced by using all density functional methods considered. However, the B3LYP and PBE0 functionals completely fail to describe the pi-->pi(*) electronic transition in solution, whereas the recent CAM-B3LYP functional performs well also in this case. The pi-->pi(*) excitation energy of acrolein in water solution is found to be very dependent on intermolecular induction and nonelectrostatic interactions. The computed excitation energies of acrolein in vacuum and solution compare well to experimental data

FIGURES 71–75 in Notes on Central Asian Furcula with description of a new species

FIGURES 71–75. Biotopes and adults of Furcula spp. in nature. 71–72. F. terminata. 71. Childara gorge, Peter I range, Darvaz, Tajikistan (8.VII.2019, photo by R. Yakovlev). 72. Tugay forest near Syr Darya river, southern Kazakhstan (25.IV.2018, photo by D. Shovkoon). 73–75. F. victoria sp. n., Kyrgyzstan. 73–74. Valley of the river Ters, Besh-Aral Nature Reserve, Chatkal range, Western Tian Shan, 1650 m (23.VI.2019, photo by P. Gorbunov). 75. Vrabat-Sai river near Chap-chima Pass, Chatkal Range, 1870 m (10.VII.2022, photo by P. Gorbunov).Published as part of <i>Morozov, Pavel S., Prozorov, Alexey M., Korb, Stanislav K., Shovkoon, Dmitry F., Gorbunov, Pavel Y., Müller, Günter C., Saldaitis, Aidas & Yakovlev, Roman V., 2023, Notes on Central Asian Furcula with description of a new species, pp. 373-388 in Zootaxa 5319 (3)</i> on page 386, DOI: 10.11646/zootaxa.5319.3.4, <a href="http://zenodo.org/record/8202988">http://zenodo.org/record/8202988</a&gt

Notes on Central Asian Furcula with description of a new species

Morozov, Pavel S., Prozorov, Alexey M., Korb, Stanislav K., Shovkoon, Dmitry F., Gorbunov, Pavel Y., Müller, Günter C., Saldaitis, Aidas, Yakovlev, Roman V. (2023): Notes on Central Asian Furcula with description of a new species. Zootaxa 5319 (3): 373-388, DOI: 10.11646/zootaxa.5319.3.4, URL: http://dx.doi.org/10.11646/zootaxa.5319.3.