Examinando por Autor "Tiznado, William"

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    Ítem
    Revisiting the potential-energy surface of CnBe3n+2H2n+22+ (n = 2–4) clusters: are planar pentacoordinate carbon structures the global minima?
    (Royal Society of Chemistry, 2023-07-07) Inostroza, Diego; Vásquez-Espinal, Alejandro; Leyva-Parra, Luis; García-Argote, Williams; Cerón, María Luisa; Yañez, Osvaldo; Tiznado, William
    Using various exploration strategies, in this study, we investigated the potential energy surfaces (PES) of CBe5H5+ and CnBe3n+2H2n+22+ (n = 2-4) clusters. Previous studies proposed that the planar pentacoordinate carbons (ppCs) were the global minima of these clusters. However, our study identified new putative global minima and competitive isomers, refuting some previous assignments. We employed several methods, including evolutive-inspired stochastic approaches guided by "chemical criteria", and ab initio molecular dynamics simulations at elevated temperatures. Our results showed that the size of the scanned population significantly affected the evolutive method and that constrained or guided procedures showed an advantage in identifying better minima for larger systems. This study demonstrated that using multiple complementary strategies can result in a wider variety of minima in a given energy range. Our findings provide valuable insights into exploring the potential energy surfaces of clusters, mainly medium-sized clusters, which could be the connections between small clusters and nanomaterials.
  • Miniatura
    Ítem
    Si6C18: a bispentalene derivative with two planar tetracoordinate carbons
    (Wiley, 2022-05-30) Inostroza, Diego; Leyva-Parra, Luis; Yañez, Osvaldo; Cruz, César J.; Garza, Jorge; García, Víctor; Thimmakondu, Venkatesan S.; Cerón, María Luisa; Tiznado, William
    Here we show that substituting the ten protons in the dianion of a bispentalene derivative (C18H102 ) by six Si2+ dications produces a minimum energy structure with two planar tetracoordinate carbons (ptC). In Si6C18, the ptCs are embedded in the terminal C5 pentagonal rings and participate in a three-center, two-electron (3c-2e) SiptC-Si σ-bond. Our exploration of the potential energy surface identifies a triphenylene derivative as the putative global minimum. Nevertheless, robustness to Born–Oppenheimer molecular dynamics (BOMD) simulations at 900 and 1500 K supports bispentalene derivative kinetic stability. Chemical bonding analysis reveals ten delocalized π-bonds, which, according to Hückel's 4n + 2 π-electron rule, would classify it as an aromatic system. Magnetically induced current density analysis reveals the presence of intense local paratropic currents and a weakly global diatropic current, the latter agreeing with the possible global aromatic character of this specie.