"Vibrational bonding": a new type of chemical bond is discovered

Fcg-Former: Identification of Functional Groups in FTIR Spectra Using Enhanced Transformer-Based Model

Deep learning (DL) is becoming more popular as a useful tool in various scientific domains, especially in chemistry applications. In the infrared spectroscopy field, where identifying functional groups in unknown compounds poses a significant challenge, there is a growing need for innovative approaches to streamline and enhance analysis processes. This study introduces a transformative approach leveraging a DL methodology based on transformer attention models. With a data set containing approximately 8677 spectra, our model utilizes self-attention mechanisms to capture complex spectral features and precisely predict 17 functional groups, outperforming conventional architectures in both functional group prediction accuracy and compound-level precision. The success of our approach underscores the potential of transformer-based methodologies in enhancing spectral analysis techniques.

Unusual Dynamics and Vibrational Fingerprints of van der Waals Dimers Formed by Linear Molecules and Rare-Gas Atoms

Detailed structural, dynamical, and vibrational analyses have been performed for systems composed of linear triatomic molecules solvated by a single rare-gas atom, He, Ne, or Ar. Among the chromophores of these van der Waals (vdW) dimers, there are four neutral molecules (CO2, CS2, N2O, and OCS) and six molecular cations (HHe2+, HNe2+, HAr2+, HHeNe+, HHeAr+, and HNeAr+), both of apolar and polar nature. Following the exploration of bonding preferences, high-level four-dimensional (4D) potential energy surfaces (PESs) have been developed for 24 vdW dimers, keeping the two intramonomer bond lengths fixed. For these 24 complexes, over 1500 bound vibrational states have been obtained via quasi-variational nuclear-motion computations, employing exact kinetic-energy operators together with the accurate 4D PESs and their 2D/3D cuts. The reduced-dimensional (2D to 4D) dimer models have been compared with full-dimensional (6D) ones in the cases of the neutral CO2·Ar and charged HHe2+·He dimers, corroborating the high accuracy of the 2D to 4D vibrational energies. The reduced-dimensional models suggest that (a) while the equilibrium structures are T-shaped and planar, the effective ground-state structures are nonplanar, (b) certain bound states belong to collinear molecular structures, even when they are not minima, (c) the vdW vibrations are heavily mixed and many states have amplitudes corresponding to both the T-shaped and collinear structures, (d) there are a few dimers, for which even some of the vdW fundamentals lie above the first dissociation limit, and (e) the vdW vibrations are almost fully decoupled from the intramonomer bending motion.

Matter - a current picture

A century ago, a two-part review by W. C. McC. Lewis entitled "The Structure of Matter" appeared in this journal, surveying the achievements that had been made to date in that field. Topics included the value of Avogadro's constant, the dimensions of a molecule, equations of state for non-ideal gases, then-current theories relating electron configurations to the Periodic Law, the then-new nuclear atom model of Rutherford, and the first findings from X-ray crystallographic studies of matter, a field then in its nascent phase. This article is a sequel to that work. As a vast quantity of research has been addressed to the topic in the intervening period, the view presented here can at best be selective and idiosyncratic. Nonetheless, it attempts to capture some of the important strides in 'matter science', broadly defined, over the past century, highlight some recent areas of interest or novelty, and give a picture of some of the mysteries that remain.

Influence of vibration in the reactive scattering of D + MuH: the effect of dynamical bonding

The dynamics of the D + MuH(v = 1) reaction has been investigated using time-independent quantum mechanical calculations. The total reaction cross sections and rate coefficients have been calculated for the two exit channels of the reaction leading, respectively, to DMu + H and DH + Mu. Over the 100-1000 K temperature range investigated the rate coefficients for the DMu + H channel are of the order of 10(-10) cm(3) s(-1) and those for the DH + Mu channel vary between 1 × 10(-12) and 8 × 10(-11) cm(3) s(-1). These results point to a virtually barrierless reaction for the DMu + H channel and to the presence of a comparatively small barrier for the DH + Mu channel and are consistent with the profiles of their respective collinear vibrationally adiabatic potentials (VAPs). The effective barrier in the VAP of the DH + Mu channel is located in the reactant valley and, consequently, translation is found to be more efficient than vibration for the promotion of the reaction over a large energy interval in the post threshold region. Below this barrier, the DH + Mu channel can be accessible through an indirect mechanism implying crossing from the DMu + H pathway. The most salient feature found in the present study is revealed in the total reaction cross section for the DMu + H channel, which shows a sharp resonance caused by the presence of a deep well in the vibrationally adiabatic potential. This well has a dynamical origin, reminiscent of that found recently in the vibrationally bonded BrMuBr complex [Fleming, et al., Angew. Chem., Int. Ed., 2014, 53, 1], and is due to the stabilizing effect of the light Mu atom oscillating between the heavier H and D isotopes and to the bond softening associated with vibrational excitation of MuH.

Muon-Substituted Malonaldehyde: Transforming a Transition State into a Stable Structure by Isotope Substitution

Isotope substitutions are usually conceived to play a marginal role on the structure and bonding pattern of molecules. However, a recent study [Angew. Chem. Int. Ed. 2014, 53, 13706-13709; Angew. Chem. 2014, 126, 13925-13929] further demonstrates that upon replacing a proton with a positively charged muon, as the lightest radioisotope of hydrogen, radical changes in the nature of the structure and bonding of certain species may take place. The present report is a primary attempt to introduce another example of structural transformation on the basis of the malonaldehyde system. Accordingly, upon replacing the proton between the two oxygen atoms of malonaldehyde with the positively charged muon a serious structural transformation is observed. By using the ab initio nuclear-electronic orbital non-Born-Oppenheimer procedure, the nuclear configuration of the muon-substituted species is derived. The resulting nuclear configuration is much more similar to the transition state of the proton transfer in malonaldehyde rather than to the stable configuration of malonaldehyde. The comparison of the "atoms in molecules" (AIM) structure of the muon-substituted malonaldehyde and the AIM structure of the stable and the transition-state configurations of malonaldehyde also unequivocally demonstrates substantial similarities of the muon-substituted malonaldehyde to the transition state.