Banca de QUALIFICAÇÃO: EDGARD FLAUZINO

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : EDGARD FLAUZINO
DATE: 17/12/2025
TIME: 09:00
LOCAL: Videoconferência
TITLE:

Chemical-Quantum Modeling of Elementary Geopolymerization Mechanisms: Influence of Counterion and Aluminum Coordination Number.

KEY WORDS:

Geopolymers; DFT; xTB; Computational Chemistry; Quantum Chemistry; QTAIM analysis

PAGES: 100
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Físico-Química
SPECIALTY: Química Teórica
SUMMARY:

The study of geopolymer formation reactions is of great importance for the development of materials for the most diverse applications.The use of experimental techniques is limited to the characterization of these materials, with little information about the reactivity of the species present in the initial stages of the geopolymerization process, in fact due to the complexity of this stage. The use of computational chemistry is used to overcome part of this limitation, providing greater understanding of the kinetics and thermodynamics of these fundamental reactions for the formation of the structure of geopolymers. The literature in this area is scarce and is limited to the study of the condensation of aluminate and silicate species without considering the effects of the interactions of alkaline activators, especially on the reaction mechanisms. Thus, through Density Functional Theory (DFT), combined with metadynamics simulations, we studied the mechanisms of the formation reactions of the oligomeric units proposed by Davidovits (1991) that are present in the initial stages of geopolymerization: orthosialate (Al-O-Si) and orthosialate-siloxo (Si-O-Al-O-Si). In particular, we studied the influence of the presence of alkaline cations from the Li⁺, Na⁺ and K⁺ series as counterions of reactive species, in addition to considering the effect of the proportion of these cations. We observed that they act as modulators and promoters of condensation between aluminate and silicate, promoting the approximation of monomers, reducing energy barriers and stabilizing the products formed. Furthermore, we observed that the coordination number of the aluminum center plays a fundamental role in the reactions. Al's versatility in changing its coordination from IV ↔ V ↔ VI enables different reaction pathways that, in the presence of counterions, lead to the growth of the polysialate chain. Finally, the characterizations of the interactions present through charge density analyses, based on the Quantum Theory of Atoms in Molecules (QTAIM), made it possible to establish a quantitative relationship between the nature of the counterion and the thermochemical properties of these systems.

COMMITTEE MEMBERS:
Interno - 1086214 - ANDERSON DOS REIS ALBUQUERQUE
Externo à Instituição - LUIZ HENRIQUE DA SILVA GASPAROTTO - UFMS
Presidente - 1859346 - MIGUEL ANGELO FONSECA DE SOUZA