José Barbosa da Silva is a PhD candidate in Biological Chemistry at URCA. He works with solid-state and computational chemistry, including DFT simulations of electronic, optical, and structural properties, as well as experimental and theoretical IR/Raman vibrational studies. His research extends to biologically active molecules, antipsychotic drugs, amino acids, and natural compounds, integrating molecular docking, molecular dynamics, and quantum biochemistry to investigate ligand–protein and membrane interactions.
EDUCATION
PhD in Biological Chemistry (ongoing)
Universidade Regional do Cariri (URCA), 2022–present
M.Sc. in Physical Chemistry (Físico-Química)
Universidade Federal do Ceará (UFC), 2018–2020
B.Sc. in Chemistry (Química)
Universidade Federal do Ceará (UFC), 2008–2016
RESEARCH, TEACHING, or OTHER INTERESTS
Chemistry, Physical and Theoretical Chemistry, Spectroscopy, Molecular Biology
10
Scopus Publications
Scopus Publications
Investigation of the structural, thermal, vibrational, and thermodynamic properties of olanzapine and risperidone crystals José Barbosa Silva, José Avelar Sousa da Silva, Antônio Medina Neto, Jurandir Fernando Comar, Ewerton Wagner Santos Caetano, Regina Claudia Rodrigues dos Santos, Mônica Belém Rodrigues, Bruno Sousa Araújo, Hélcio Silva dos Santos, Valder Nogueira Freire, Alexandre Magno Rodrigues Teixeira Journal of Molecular Structure, 2026 • The combined experimental–theoretical framework elucidate olanzapine and risperidone's solid-state behavior. • Dispersion-corrected DFT accurately reproduces experimental crystal structures. • Crystal lattice dynamics provide a solid-state basis for drug stability. • Low-frequency lattice modes govern thermal behavior of olanzapine and risperidone. • Hydrogen-bond topology controls lattice thermodynamics in both drugs. Olanzapine and risperidone are widely used antipsychotics whose solid-state properties are governed by crystal packing and low-energy lattice dynamics. Here, we combine powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), and infrared/Raman spectroscopy with dispersion-inclusive periodic density functional theory (DFT) and density-functional perturbation theory (DFPT) calculations to establish a consistent vibrational, phonon, and thermodynamic description of their crystalline forms. Bulk structure optimizations performed at LDA, GGA-PBE, and GGA+TS levels support the importance of van der Waals interactions for accurate molecular-crystal geometries, while simulated IR/Raman spectra enable mode assignments based on phonon eigenvectors across three spectral windows (0–900, 900–1800, and 2750–3250 cm −1 ). Phonon dispersion relations are computed along selected high-symmetry directions, with emphasis on the 0–100 cm −1 region to highlight lattice modes most relevant to thermal behavior. From the phonon spectrum, we derive temperature-dependent thermodynamic functions, including Debye temperature ΘD(T), constant-volume heat capacity CV(T), vibrational enthalpy Hvib(T), Helmholtz free energy Fvib(T), and the entropic contribution TSvib(T) over 0–1000 K. The results reveal systematic differences between olanzapine and risperidone consistent with distinct low-frequency mode distributions and vibrational phase space, providing a microscopic basis for comparative thermal trends. Risperidone exhibits a higher density of low-frequency lattice modes and, consequently, larger phonon-derived entropic and heat-capacity responses than olanzapine across the investigated temperature range. Overall, this study delivers an integrated experimental–theoretical framework that advances solid-form identification, packing-sensitive vibrational fingerprinting, and phonon-based thermodynamic interpretation in pharmaceutical molecular crystals.
Structural, Electronic, and Optical Properties of Monoclinic Pharmaceutical Crystals: A DFT Study of Salicylic Acid, Acetylsalicylic Acid, Acetaminophen, and Ibuprofen Liciane L. Ferreira, Mariana S. Alves, Micael E. P Oliveira, Valder N. Freire, Bruno P. Silva, José B. Silva, Ewerton W. S. Caetano ACS Omega, 2026 The solid-state properties of pharmaceutical compounds play a critical role in their therapeutic efficacy, influencing their solubility, bioavailability, and stability. In this study, we investigate the monoclinic crystalline forms of four widely used anti-inflammatory drugssalicylic acid, acetylsalicylic acid (aspirin), acetaminophen (paracetamol), and ibuprofenusing density functional theory (DFT). Employing the Perdew, Burke, and Ernzerhof (PBE) functional with Tkatchenko-Scheffler dispersion correction, we performed geometry optimizations of the unit cells, achieving lattice parameters within 1-2% of experimental values. Time-dependent DFT (TD-DFT) calculations revealed molecular UV-vis absorption spectra consistent with experimental data, elucidating key electronic transitions. Kohn-Sham band structure analyses using the HLE17 functional identified indirect band gaps ranging from 2.99 eV (salicylic acid) to 4.02 eV (ibuprofen) with near-direct transitions suggesting potential optical activity. For the acetylsalicylic acid crystal, the calculated optical absorption spectrum reproduces the main experimental features after a rigid energy shift, highlighting the effectiveness and limitations of the DFT-PBE + TS approach for describing its optical properties. Optical absorption and dielectric function calculations for light polarized along the (100), (010), and (001) crystal directions highlighted anisotropic responses tied to crystal packing and hydrogen-bonding networks. These findings provide a comprehensive understanding of the interplay among the molecular structure, crystal lattice, and optoelectronic properties, offering insights and providing a theoretical foundation for the rational design of pharmaceutical formulations with enhanced performance.
Vibrational spectroscopy and phonon-related properties of monoclinic GABA, a non-proteinogenic inhibitory neurotransmitter amino acid José Barbosa Silva, Gabriel Costa, Mauricélio Bezerra da Silva, Stefane Nunes Costa, Regina Cláudia Rodrigues dos Santos, Francisco Adilson Matos Sales, Antoninho Valentini, Ewerton Wagner Santos Caetano, Valder Nogueira Freire Journal of Raman Spectroscopy, 2021 The γ‐aminobutyric acid (GABA) is the most important inhibitory neurotransmitter in vertebrate central nervous systems. Taking full account of the measured X‐ray diffractogram of its stable monoclinic polymorph, we have performed density functional theory (DFT) calculations to analyze/understand its infrared and Raman spectra considering its monoclinic polymorph, an isolated stabilized (120) plane, and a single GABA molecule. Besides, phonon dispersion/density of states, heat capacity, Debye temperature, and entropy/enthalpy/free energies were also obtained for the GABA monoclinic crystal. Vibrational signatures due to the GABA (120) planes are pointed out for the first time for several wavenumbers. The results obtained for the GABA monoclinic polymorph reinforce the need of dispersion‐corrected solid‐state calculations to describe the vibrational properties of molecular crystals instead of considering a single isolated molecule picture, even for wavenumbers larger than those usually associated with lattice modes.
