Optical absorption and DFT calculations in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>L</mml:mi></mml:math>-aspartic acid anhydrous crystals: Charge carrier effective masses point to semiconducting behavior

Silva, A. M.; Silva, B. P.; Sales, Francisco Adilson Matos; Freire, V. N.; Moreira, E.; Fulco, U. L.; Albuquerque, E.L.; Maia, F. F.; Caetano, E. W. S.

doi:10.1103/physrevb.86.195201

Cited by 53 publications

(25 citation statements)

References 60 publications

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“…The Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm is used to relax the structure of the crystal models. The generalized gradient approximation (GGA) parametrized by Perdew, Burke, and Ernzerhof (PBE) are used to calculate the exchange-correlation energy [20,21]. Through a series of convergence tests, the energy cut-off is established as 500eV.…”

Section: Calculation Methods and Calculation Modelmentioning

confidence: 99%

“…The convergence energy change is set less than 2×10 -6 eV/atom, the convergence force is less than 0.005eV/nm, the stress less than 0.05GPa, and the change in displacement less than 0.00001nm. The Brillouin zone [21] integral is sampled with the Monkhorst-Pack mesh [22] scheme and special k points of high symmetry. The number of k-points needed for Al 0.5 Ga 0.5 As (001) and Al 0.25 Ga 0.75 N (0001) surface are set as 4×6×1 and 6×6×1 respectively.…”

Section: Calculation Methods and Calculation Modelmentioning

confidence: 99%

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Comparative Research on Cs Activation Mechanism for Al0.5Ga0.5As (001) and Al0.25Ga0.75N (0001) Surface

Shen

Chen

et al. 2015

IEEE Sensors J.

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To investigate and distinguish the difference of Cs activation mechanism on Al 0.5 Ga 0.5 As (001) and Al 0.25 Ga 0.75 N (0001) surface, plane wave with ultrasoft pseudopotential method based on first-principle density functional theory (DFT) is used. Surface adsorption energy, work function and surface dipole moments with different Cs coverage are calculated and compared. Eight possible Cs adsorption sites are chosen for the Al 0.5 Ga 0.5 As (001) surface while seven high-symmetry sites are considered in the calculation model of Al 0.25 Ga 0.75 N (0001) surface. Results show that when only one Cs atom adsorbed on two surfaces, the adsorption energies are all negative and the adsorption sites are all stable sites. The lowest work function and the most stable adsorption sites with different Cs coverage are obtained and discussed. When different amounts of Cs atoms adsorbed on two surfaces, the work function values of Al 0.25 Ga 0.75 N (0001) surface are all smaller than that of Al 0.5 Ga 0.5 As (001) surface. The work function of Al 0.5 Ga 0.5 As (001) surface decreases with the increase of Cs coverage when the Cs coverage changes from 0 monolayer (ML) to 0.75 ML, while Al 0.25 Ga 0.75 N (0001) surface achieves the smallest work function when the Cs coverage is 0.5 ML. Finally, photocurrent curves during Cs activation are recorded. The photocurrent of AlGaAs sample reaches at a peak at the time of 29 min when the Cs coverage rise at 0.75 ML, while the photocurrent of AlGaN sample achieves a peak at the time of 30 min when the Cs coverage rise at 0.5 ML, which is in well consistent with our calculation results.

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Section: Calculation Methods and Calculation Modelmentioning

confidence: 99%

Section: Calculation Methods and Calculation Modelmentioning

confidence: 99%

Comparative Research on Cs Activation Mechanism for Al0.5Ga0.5As (001) and Al0.25Ga0.75N (0001) Surface

Shen

Chen

et al. 2015

IEEE Sensors J.

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“…The plane-wave ultra-soft pseudopotential method [18] based on DFT within the generalized-gradient approximation (GGA) [19,20] is used. All calculations are carried in reciprocal space and the atomic pseudopotentials, described by ultra-soft pseudopotential [21,22], are generated from the following electronic configurations as: Ga: 3d 10 4s 2 4p 1 , Al: 3s 2 3p 1 , As: 4s 2 4p 3 , N: 2s 2 2p 3 , Cs: 5s 2 5p 6 6s 1 and H: 1s. The Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm is used to http://dx.doi.org/10.1016/j.apsusc.2014.…”

Section: Calculation Methods and Modelsmentioning

confidence: 99%

Research on Cs activation mechanism for Ga0.5Al0.5As(001) and GaN(0001) surface

Shen¹,

Chen²,

Qian³

et al. 2015

Applied Surface Science

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“…[17][18][19][20][21][22][23][24] As members of the class of molecular crystals, anhydrous monoclinic and monohydrated orthorhombic asparagine crystals are stabilized by hydrogen bonds and van der Waals interactions which determine their structural, electronic, optical, and vibrational properties. Research on molecular crystals has being somewhat restricted to experimental characterization of their polymorphs through infrared, Raman, nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR) spectroscopies, which are very useful in the pharmaceutical domain, for example.…”

Section: Introductionmentioning

confidence: 99%

“…Among the few reports already published concerning the field of amino acid crystal simulations, some of them have presented results suggesting that alanine, leucine, isoleucine, and glycine [17][18][19] are wide band gap semiconductors, while valine and cysteine could be small band gap isolators; 17, 20 on the other hand, it was suggested that anhydrous L-aspartic crystals behave as wide-gap semiconductors with higher carrier mobilities for directions parallel to the L-aspartic acid molecular layers, 21 while anhydrous L-serine crystals behave like n-type wide gap semiconductors. 22 Besides, it was also pointed out that anhydrous crystals of DNA bases are wide gap semiconductors.…”

Section: Introductionmentioning

confidence: 99%

L-asparagine crystals with wide gap semiconductor features: Optical absorption measurements and density functional theory computations

Zanatta

Gottfried

Silva

et al. 2014

The Journal of Chemical Physics

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Results of optical absorption measurements are presented together with calculated structural, electronic, and optical properties for the anhydrous monoclinic L-asparagine crystal. Density functional theory (DFT) within the generalized gradient approximation (GGA) including dispersion effects (TS, Grimme) was employed to perform the calculations. The optical absorption measurements revealed that the anhydrous monoclinic L-asparagine crystal is a wide band gap material with 4.95 eV main gap energy. DFT-GGA+TS simulations, on the other hand, produced structural parameters in very good agreement with X-ray data. The lattice parameter differences Δa, Δb, Δc between theory and experiment were as small as 0.020, 0.051, and 0.022 Å, respectively. The calculated band gap energy is smaller than the experimental data by about 15%, with a 4.23 eV indirect band gap corresponding to Z → Γ and Z → β transitions. Three other indirect band gaps of 4.30 eV, 4.32 eV, and 4.36 eV are assigned to α3 → Γ, α1 → Γ, and α2 → Γ transitions, respectively. Δ-sol computations, on the other hand, predict a main band gap of 5.00 eV, just 50 meV above the experimental value. Electronic wavefunctions mainly originating from O 2p-carboxyl, C 2p-side chain, and C 2p-carboxyl orbitals contribute most significantly to the highest valence and lowest conduction energy bands, respectively. By varying the lattice parameters from their converged equilibrium values, we show that the unit cell is less stiff along the b direction than for the a and c directions. Effective mass calculations suggest that hole transport behavior is more anisotropic than electron transport, but the mass values allow for some charge mobility except along a direction perpendicular to the molecular layers of L-asparagine which form the crystal, so anhydrous monoclinic L-asparagine crystals could behave as wide gap semiconductors. Finally, the calculations point to a high degree of optical anisotropy for the absorption and complex dielectric function, with more structured curves for incident light polarized along the 100 and 101 directions.

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Optical absorption and DFT calculations inL-aspartic acid anhydrous crystals: Charge carrier effective masses point to semiconducting behavior

Cited by 53 publications

References 60 publications

Comparative Research on Cs Activation Mechanism for Al<sub>0.5</sub>Ga<sub>0.5</sub>As (001) and Al<sub>0.25</sub>Ga<sub>0.75</sub>N (0001) Surface

Comparative Research on Cs Activation Mechanism for Al<sub>0.5</sub>Ga<sub>0.5</sub>As (001) and Al<sub>0.25</sub>Ga<sub>0.75</sub>N (0001) Surface

Research on Cs activation mechanism for Ga0.5Al0.5As(001) and GaN(0001) surface

L-asparagine crystals with wide gap semiconductor features: Optical absorption measurements and density functional theory computations

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