arXiv subjects

Yulia V. Novakovskaya

Publications and source records attributed to Yulia V. Novakovskaya.

5 recordsLinked to original sources

arXiv2024

σ/π character of H-bonding in water clusters

Hydrogen bonds are typically treated as sufficiently localized directional intermolecular bonds, in which dispersion and electrostatic contributions can be distinguished. However, being formed chiefly due to the overlapping of p orbitals of electronegative atoms, the corresponding electronic bonds are characterized by both σ- and π-kind binding, the former determining the directionality of bonds, while the latter, the coupling of molecules and the collective effects in H-bond networks. The latter contribution was never considered previously and is predetermined by overlapping pre-lone pair orbitals of oxygen atoms. This is manifested in the peculiarities of the electron density distribution, which are quantified based on the analysis of magnetic shielding tensors of oxygen and bridge hydrogen nuclei and illustrated by the shapes of cluster orbitals of water aggregates.

physics.chem-ph↗

arXiv2022

Acidity of graphene oxide aqueous solutions: the role of hydroxyls unveiled

Nonempirical modeling of hydrated single-layer graphene oxide (GO) fragments revealed that at least one, but substantial origin of the acidity of aqueous GO solutions is the dissociation in closely grouped and favorably H-bonded hydroxyls. The process can further be promoted by the adjacent $π$-conjugated carbon segments at the edges of GO flakes or their inner defects. The apparent $pK_a$ values of the groups fall in a range of ca. 2.0 to 5.3. Under certain conditions the ionization may become spontaneous.

cond-mat.mtrl-sci↗

arXiv2021

3-Aminopropanol: polymolecular structures that determine unique solvation motifs

Intermolecular bonding of 3-aminopropanol (3-AP) molecules is discussed in comparison to 2-aminopropanol (2-AP) and 2-aminoethamol (2-AE). The consideration is based on the results of nonempirical quantum chemical simulations of the molecular clusters carried out at the MP2/6-31+G(d,p) level. Particular attention is paid to the formation of variously ordered 3-AP aggregates, which can be doubled or bracelet rings, extended chains, ribbons, or double helices, impossible in the case of any close amino alcohol analogue, but favorable for the solvation of diverse either hydrophilic or hydrophobic species.

physics.atm-clus↗

arXiv2021

Flexibility and regularity of the hydration structure of a sodium ion. Nonempirical insight

The stationary nonempirical simulations of Na+(H2O)n clusters with n in a range of 28 to 51 carried out at the density functional level with a hybrid B3LYP functional and the Born-Oppenheimer molecular dynamics modeling of the size selected clusters reveal the interrelated structural and energetic peculiarities of sodium hydration structures. Surface, bulk, and transient configurations of the clusters are distinguished with the different location of the sodium nucleus (close to either the spatial center of the structure or one of its side faces) and its consistently changing coordination number (which typically equals five or six). The mean Na-O distances for the first-shell water molecules are found to depend both on the spatial character of the structure and the local coordination of sodium. The values are compared to different experimental estimates, and the virtual discrepancy of the latter is explained based on the results of the cluster simulations. Different coordination neighborhoods of sodium are predicted depending on its local fraction in the actual specimens.

physics.chem-ph↗

arXiv2012

Conjugation in hydrogen-bonded systems

Analysis of the electron density distribution in clusters composed of hydrogen fluoride, water, and ammonia molecules, especially within the hydrogen-bond domains, reveals the existence of both σ- and π-binding between molecules. The σ-kind density distribution determines the mutual orientation of molecules. A π-system may be delocalized conjugated, which provides additional stabilization of molecular clusters. In those clusters where the sequence of hydrogen bonds is not planar, a peculiar kind of π-conjugation exists. HF anion and H5O2 cation are characterized by quasi-triple bonds between the electronegative atoms. The most long-lived species stabilized by delocalized π-binding are rings and open or closed hoops composed of fused rings. It is conjugated π-system that determines cooperativity phenomenon.

physics.chem-ph↗