Probing the Electronic Structure and Property of Neutral and Charged Arsenic Clusters (Asn(+1,0,–1), n ≤ 8) Using Gaussian-3 Theory

Stabilization mechanism of arsenic-sulfide slag by density functional theory calculation of arsenic-sulfide clusters

Stabilization of arsenic sulfur slag (As‒S slag) is of high importance to prevent the release of deadly As pollutants into environment. However, the molecular understanding on the stability of As‒S slag is missing, which in turn restricts the development of robust approach to solve the challenge. In this work, we investigated the structure-stability relationship of As‒S slag with adopting various As‒S clusters as prototypes by density functional theory (DFT). Results showed that the configuration of S multimers-covering-(As₂S₃)_n is the most stable structure amongst the candidates by the analysis of energies and bonding characteristics. The high stability is explained by orbital composition that the 4p-orbital (As) binding with 3p-orbital (S) decreases energy level of highest occupied molecular orbital (HOMO). Inspired from the calculations, an excess-S-based hydrothermal method was successfully proposed and achieved to promote the stabilization of As‒S slag. Typically, the As concentration from the leaching test of stabilized As‒S slag is only 0.8 mg/L, which is much lower than the value from other stabilized slag.

First-Principles Studies on the Structural and Electronic Properties of As Clusters

Based on the genetic algorithm (GA) incorporated with density functional theory (DFT) calculations, the structural and electronic properties of neutral and charged arsenic clusters As_n (n = 2–24) are investigated. The size-dependent physical properties of neutral clusters, such as the binding energy, HOMO-LUMO gap, and second difference of cluster energies, are discussed. The supercluster structures based on the As₈ unit and As₂ bridge are found to be dominant for the larger cluster As_n (n ≥ 8). Furthermore, the possible geometric structures of As₂₈, As₃₈, and As₁₈₀ are predicted based on the growth pattern.

Laser Desorption Ionization of As2Ch3 (Ch = S, Se, and Te) Chalcogenides Using Quadrupole Ion Trap Time-of-Flight Mass Spectrometry: A Comparative Study

Laser desorption ionization using time-of-flight mass spectrometer afforded with quadrupole ion trap was used to study As₂Ch₃ (Ch = S, Se, and Te) bulk chalcogenide materials. The main goal of the study is the identification of species present in the plasma originating from the interaction of laser pulses with solid state material. The generated clusters in both positive and negative ion mode are identified as 10 unary (S _p^+/- and As _m^+/- ) and 34 binary (As _m S _p^+/- ) species for As₂S₃ glass, 2 unary (Se _q^+/- ) and 26 binary (As _m Se _q^+/- ) species for As₂Se₃ glass, 7 unary (Te _r^+/- ) and 23 binary (As _m Te _r^+/- ) species for As₂Te₃ material. The fragmentation of chalcogenide materials was diminished using some polymers and in this way 45 new, higher mass clusters have been detected. This novel approach opens a new possibility for laser desorption ionization mass spectrometry analysis of chalcogenides as well as other materials. Graphical abstract ᅟ.

Study on electronic structures and properties of neutral and charged arsenic sulfides [As n S3 ((-1,0,+1)), n =1-6] with the Gaussian-3 scheme

The structures and energies of neutral and charged arsenic sulfides As n S3 ((-1,0,+1)) (n = 1-6) were studied systematically with the G3 method. The ground-state structures of these species are reported. The ground-state structures of As n S3 with n ≥ 4 can be considered as resulting from the replacement of an As atom of the ground-state structure of neutral As n+1S2 by an S atom. In neutral As n S3, the character of sulfur bonding is edge-bridging. The ground-state structures of anion As n S3 (-) sometimes differ from their corresponding neutral structures. In such case, they exhibit a terminal sulfur atom. The ground-state structures of cationic As n S3 (+) are also sometimes different from the corresponding neutral ones. There, sulfur bonding can exhibit face-capping and arsenic can be four-fold coordinated. The potential energy surfaces of As4S3 (+) and As5S3 (+) are very flat and co-existence of various isomers of As4S3 (+) and As5S3 (+) is possible. Reliable adiabatic electron affinities (AEAs) and adiabatic ionization potentials (AIPs) of As n S3 are predicted. There are odd-even alternations in both AEAs and AIPs as a function of size. In addition, the reliable vertical detachment energies (VDEs) and vertical ionization potentials (VIPs) are presented. The dissociation energies (DEs) of S (and/or its ion S((-/+))) from As n S3 species and their ions were calculated to examine relative stabilities. The hardnesses and HOMO-LUMO gaps of As n S3 (n = 1-6) were evaluated and used to discuss relative chemical reactivity.

A Gaussian-3 theoretical study of the alkylthio radicals and their anions: structures, thermochemistry, and electron affinities

The optimized geometries, electron affinities, and dissociation energies of the alkylthio radicals have been determined with the higher level of the Gaussian-3(G3) theory. The geometries are fully optimized and discussed. The reliable adiabatic electron affinities with ZPVE correction have been predicted to be 1.860 eV for the methylthio radical, 1.960 eV for the ethylthio radical, 1.980 and 2.074 eV for the two isomers (n-C3H7S and i-C3H7S) of the propylthio radical, 1.991, 2.133 and 2.013 eV for the three isomers (n-C4H9S, t-C4H9S, and i-C4H9S) of the butylthio radical, and 1.999, 2.147, 2.164, and 2.059 eV for the four isomers (n-C5H11S, b-C5H11S, c-C5H11S, and d-C5H11S) of the pentylthio radical, respectively. These corrected EAad values for the alkylthio radicals are in good agreement with available experiments, and the average absolute error of the G3 method is 0.041 eV. The dissociation energies of S atom from neutral CnH2n+1S (n = 1-5) and S(-) from corresponding anions CnH2n+1S(-) species have also been estimated respectively to examine their relative stabilities.