%0 Journal Article %1 WOS:000310684100008 %A Silva, A M %A Silva, B P %A Sales, F A M %A Freire, V N %A Moreira, E %A Fulco, U L %A Albuquerque, E L %A Jr., F F Maia %A Caetano, E W S %C ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA %D 2012 %I AMER PHYSICAL SOC %J PHYSICAL REVIEW B %K imported %N 19 %R 10.1103/PhysRevB.86.195201 %T Optical absorption and DFT calculations in L-aspartic acid anhydrous crystals: Charge carrier effective masses point to semiconducting behavior %V 86 %X Density functional theory (DFT) computations within the local-density approximation and generalized gradient approximation in pure form and with dispersion correction (GGA + D) were carried out to investigate the structural, electronic, and optical properties of L-aspartic acid anhydrous crystals. The electronic (band structure and density of states) and optical absorption properties were used to interpret the light absorption measurements we have performed in L-aspartic acid anhydrous crystalline powder at room temperature. We show the important role of the layered spatial disposition of L-aspartic acid molecules in anhydrous L-aspartic crystals to explain the observed electronic and optical properties. There is good agreement between the GGA + D calculated and experimental lattice parameters, with (Delta a, Delta b, Delta c) deviations of (0.029, - 0.023, - 0.024) (units in angstrom). Mulliken J. Chem. Phys. 23, 1833 (1955) and Hirshfeld Theor. Chim. Acta 44, 129 (1977) population analyses were also performed to assess the degree of charge polarization in the zwitterion state of the L-aspartic acid molecules in the DFT converged crystal. The lowest-energy optical absorption peaks related to transitions between the top of the valence band and the bottom of the conduction band involve O 2p valence states and C 1p and O 2p conduction states, with the carboxyl and COOH lateral chain group contributing significantly to the energy band gap. Among the calculated band gaps, the lowest GGA + D (4.49-eV) gap is smaller than the experimental estimate of 5.02 eV, as obtained by optical absorption. Such a wide-band-gap energy together with the small carrier effective masses estimated from band curvatures allows us to suggest that an L-aspartic acid anhydrous crystal can behave as a wide-gap semiconductor. A comparison of effective masses among directions parallel and perpendicular to the L-aspartic molecules layers reveals that charge transport must be favored in the former case. Finally, we also show that there is a strong optical anisotropy in the dielectric function of L-aspartic acid anhydrous crystals.

@article{WOS:000310684100008, abstract = {Density functional theory (DFT) computations within the local-density approximation and generalized gradient approximation in pure form and with dispersion correction (GGA + D) were carried out to investigate the structural, electronic, and optical properties of L-aspartic acid anhydrous crystals. The electronic (band structure and density of states) and optical absorption properties were used to interpret the light absorption measurements we have performed in L-aspartic acid anhydrous crystalline powder at room temperature. We show the important role of the layered spatial disposition of L-aspartic acid molecules in anhydrous L-aspartic crystals to explain the observed electronic and optical properties. There is good agreement between the GGA + D calculated and experimental lattice parameters, with (Delta a, Delta b, Delta c) deviations of (0.029, - 0.023, - 0.024) (units in angstrom). Mulliken [J. Chem. Phys. 23, 1833 (1955)] and Hirshfeld [Theor. Chim. Acta 44, 129 (1977)] population analyses were also performed to assess the degree of charge polarization in the zwitterion state of the L-aspartic acid molecules in the DFT converged crystal. The lowest-energy optical absorption peaks related to transitions between the top of the valence band and the bottom of the conduction band involve O 2p valence states and C 1p and O 2p conduction states, with the carboxyl and COOH lateral chain group contributing significantly to the energy band gap. Among the calculated band gaps, the lowest GGA + D (4.49-eV) gap is smaller than the experimental estimate of 5.02 eV, as obtained by optical absorption. Such a wide-band-gap energy together with the small carrier effective masses estimated from band curvatures allows us to suggest that an L-aspartic acid anhydrous crystal can behave as a wide-gap semiconductor. A comparison of effective masses among directions parallel and perpendicular to the L-aspartic molecules layers reveals that charge transport must be favored in the former case. Finally, we also show that there is a strong optical anisotropy in the dielectric function of L-aspartic acid anhydrous crystals.}, added-at = {2022-05-23T20:00:14.000+0200}, address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA}, author = {Silva, A M and Silva, B P and Sales, F A M and Freire, V N and Moreira, E and Fulco, U L and Albuquerque, E L and Jr., F F Maia and Caetano, E W S}, biburl = {https://www.bibsonomy.org/bibtex/2a5251e7dca4d95002f2670387638362b/ppgfis_ufc_br}, doi = {10.1103/PhysRevB.86.195201}, interhash = {9895d1c04f485bfd49c6a277986f3f91}, intrahash = {a5251e7dca4d95002f2670387638362b}, issn = {2469-9950}, journal = {PHYSICAL REVIEW B}, keywords = {imported}, number = 19, publisher = {AMER PHYSICAL SOC}, pubstate = {published}, timestamp = {2022-05-23T20:00:14.000+0200}, title = {Optical absorption and DFT calculations in L-aspartic acid anhydrous crystals: Charge carrier effective masses point to semiconducting behavior}, tppubtype = {article}, volume = 86, year = 2012 }