Navegando por Autor "Costa, Cleidinéia Cavalcante da"

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    Ab initio molecular dynamics simulation of methanol and acetonitrile : the effect of van der Waals interactions.
    (2019) Resende, Rafael Fanni Dias; Costa, Cleidinéia Cavalcante da; Manhabosco, Taíse Matte; Oliveira, Alan Barros de; Matos, Matheus Josué de Souza; Soares, Jaqueline dos Santos; Batista, Ronaldo Junio Campos
    We employed PBE and BLYP semi-local functionals and the van der Waals density functional of Dion et al. (2004) (vdW-DF) to investigate structural properties of liquid acetonitrile and methanol. Among those functionals the vdW-DF is the only one that correctly predicts energy minima in inter-molecular interactions between acetonitrile molecules. We found that van der Waals interactions have a negligible effect on H-bonds in methanol chains. However, it significantly increases chain packing resulting in a more dense liquid in comparison to the other two functionals. The overall trend is that the vdW-DF tends to overestimate density and bulk modulus, meanwhile the semi-local functionals tend to underestimate density. Thus, van der Waals interactions play an important role in the properties of liquids in which much stronger dipole-dipole interactions are present.
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    Dinâmica ab initio de líquidos polares : acetonitrila e metanol.
    (2014) Costa, Cleidinéia Cavalcante da; Batista, Ronaldo Junio Campos; Manhabosco, Taíse Matte; Oliveira, Alan Barros de; Mota, Vinícius Cândido
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    The use of complex impedance spectroscopy measurements for improving strain sensor performance.
    (2019) Mapa, Ludmila Marotta; Golin, Alana Fernandes; Costa, Cleidinéia Cavalcante da; Bianchi, Rodrigo Fernando
    Ultrasensitive strain sensors have significant practical application in human-motion detection. However, there is still a challenge for developing strain sensors that are capable of detecting high strain and a high gauge factor (GF). The aim of this study was to investigate whether a semiconducting polymer and AC measurements are able to improve the GF of stretchable sensors. We employed complex impedance spectroscopy measurements to adjust the optimal operating frequency and the impedance component for improving the device performance of a polyaniline film on a flexible poly(vinyl chloride):diisononyl phthalate sub-strate. In the DC regime,the sensor revealed linearity and GF ∼18 at 46% strain. oreover,the frequency of 100 Hz corresponds to the ideal work re- gion to operate the device that unifies sensitivity and linearity, as well as to directly correlate GF and Z∗(100) data. The most surprising correlation is with GF from Z”(100), i.e. GF”(100), which is about 9 times higher than GF (DC regime) at 46% strain. The ColeDavidson approach is developed, in which Z’(f) and Z”(f) are calculated as functions of tensile stress. This model provides the correlation between GF”(100) and the electrical resistance and capacitance of the device, as well as the charge-carrier hopping distance dependence on the tensile stress.