Study on Structure and Property of Lutetium Introduced Silicon Clusters LuSi n (n = 3–10) and Their Anions with Density Functional Theory

NWPEsSe: An Adaptive-Learning Global Optimization Algorithm for Nanosized Cluster Systems

Global optimization constitutes an important and fundamental problem in theoretical studies in many chemical fields, such as catalysis, materials, or separations problems. In this paper, a novel algorithm has been developed for the global optimization of large systems including neat and ligated clusters in the gas phase and supported clusters in periodic boundary conditions. The method is based on an updated artificial bee colony (ABC) algorithm method, that allows for adaptive-learning during the search process. The new algorithm is tested against four classes of systems of diverse chemical nature: gas phase Au₅₅, ligated Au₈²⁺, Au₈ supported on graphene oxide and defected rutile, and a large cluster assembly [Co₆Te₈(PEt₃)₆][C₆₀]_n, with sizes ranging between 1 and 3 nm and containing up to 1300 atoms. Reliable global minima (GMs) are obtained for all cases, either confirming published data or reporting new lower energy structures. The algorithm and interface to other codes in the form of an independent program, Northwest Potential Energy Search Engine (NWPEsSe), is freely available, and it provides a powerful and efficient approach for global optimization of nanosized cluster systems.

Solvation of lithium ion in helium clusters: Structural properties and relative stabilities

Structural study and relative stabilities of Li⁺-doped helium clusters Li⁺He_n (n = 1-18) has been reported in this work using two theoretical protocols. The first one is based on the basin-hopping optimization technique, where the total energy of each cluster is described by an additive model describing Li⁺-He and He-He interactions. The second one is the DFT calculations, in which the initial structures are generated by ABCluster algorithm and CALYPSO software. The CSA shape was found where the first solvation shell is completed at n = 10. The relative stabilities of Li⁺He_n (n = 1-18) clusters have been discussed based on the variation of the binding energy, second-order difference in energy, fragmentation energy and HOMO-LUMO energy gap as a function of the cluster size. The results showed that Li⁺He₁₀ is the most stable cluster. The dipole moment is calculated and showed the polar character of the Li⁺He_n clusters. Finally, the interatomic interactions have been examined topologically by the means of AIM and non-covalent reduced density gradient (NC-RDG) analyses.

A density functional theory study of the molecular interactions between a series of amides and sulfuric acid

Amides, a class of nitrogen-containing organic pollutants in the atmosphere, may affect the formation of atmospheric aerosols by the interactions with sulfuric acid. Here, the molecular interactions of sulfuric acid with formamide, methylformamide, dimethylformamide, acetamide, methylacetamide and dimethylacetamide was investigated by density functional theory. Geometry optimization and Gibbs free energy calculation were carried out at M06-2X/6-311++G(3df,3pd) level. The results indicate that the addition of amides to H₂SO₄ might have a promoting effect on atmospheric new particle formation at 298.15 K and 1 atm. In the initial stage of new particle formation, the binding capacity of amides and sulfuric acid is stronger than ammonia, but weaker than methylamine. It is worth noting that the trans-methylacetamide could have similar capabilities of stabilizing sulfuric acid as dimethylamine. In the presence of water, amides are found to only have a weak enhancement capability on new particle formation. In addition, we can infer from evaporation rate that the small molecule clusters of formamide and sulfuric acid may be more energetically favorable than macromolecule clusters.