Atomic simulations and prediction of NMR spectra in carbonaceous materials.

Name: Alan Johnny Romanel Ambrozio
Type: PhD thesis
Publication date: 13/07/2018
Advisor:

Namesort descending Role
Jair Carlos Checon de Freitas Advisor *
Wanderlã Luis Scopel Co-advisor *

Examining board:

Namesort descending Role
Alexandre Amaral Leitão External Examiner *
Arlan da Silva Gonçalves External Examiner *
Jair Carlos Checon de Freitas Advisor *
Jorge Luis Gonzalez Alfonso Internal Examiner *
Vinícius Cândido Mota Internal Examiner *
Wanderlã Luis Scopel Co advisor *
Wendel Silva Paz External Examiner *

Summary: In this work, the 13C NMR spectral parameters of both ordered and disordered carbon materials were calculated using computational simulations. The 13C NMR shielding in a single graphene sheet was calculated using density functional theory (DFT) via the gauge-including projector augmented plane wave (GIPAW) method. After performing convergence tests involving changes of k-sampling and supercell
size, the calculations were extended to graphene-based systems, including graphene bilayer and stacked graphene sheets, finally leading to hexagonal graphite. Regarding the disordered carbon materials, the 13C NMR chemical shifts corresponding to different sites in atomistic models of amorphous hydrogenated carbons were also computed at different H contents by employing molecular dynamics and firstprinciples
methods. The models were validated by the pair distribution functions
and further bonding analyses were carried out to determine the amounts of sp3 and sp2 carbons in the structures. Specifically, the obtained results allowed the distinction of the chemical shifts associated with different types of carbon sites, with different hybridization states and bonded or not to a hydrogen atom. The calculated results showed good agreement with experimental 13C NMR spectra of different types of
carbon materials, evidencing the power of the DFT calculations to predict NMR parameters in graphene-based nanocarbons and to identify local structural features of disordered carbon materials.

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