Density Functional Calculations on the Metal-Polymer Interfaces

1993 ◽  
Vol 304 ◽  
Author(s):  
A. Selmani ◽  
A. Ouhlal ◽  
A. Yelon
Keyword(s):  
Density Functional ◽  
Vibrational Analysis ◽  
Density Functional Theory Calculations ◽  
Energy Difference ◽  
Stable Configuration ◽  
Polymer Interfaces ◽  
Functional Theory ◽  
Model Molecule ◽  
Spin Polarisation ◽  
Metal Polymer

AbstractBonding of chromium to the polyimide, PMDA-ODA, surface is still subject to debate. In an attempt to clarify this problem, we have performed density functional theory calculations on a model molecule, phthalimide, which contains the most reactive functionalities of the polyimide PMDA part. Considering only the low spin case, we find that chromium bonds preferentially to the phenyl ring. However, when we release the spin polarisation and optimise the structure, we find that the absolute stable configuration is that of chromium in a quintet state at a carbonyl group. The energy difference is 0.30 eV. The complete optimised structures are determined. The infrared spectrum have been calculated for phthalimide and compared to experimental spectra. The agreement is excellent. A vibrational analysis for the Cr/phthalimide system, in both configurations (Cr on C=O and Cr on phenyl), in their stable spin states, is presented.

scholarly journals Density-Functional-Theory Calculations of Formation Energy of the Nitrogen-Doped Diamond

2018 ◽  
Vol 18 (4) ◽  
pp. 749 ◽  
Author(s):  
Sholihun Sholihun ◽  
Hana Pratiwi Kadarisman ◽  
Pekik Nurwantoro
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Formation Energy ◽  
Geometry Optimization ◽  
Density Functional Theory Calculations ◽  
Energy Difference ◽  
Stable Configuration ◽  
Functional Theory ◽  
Substitutional Site ◽  
Nitrogen Doped

The geometry optimization of the nitrogen-doped diamond has been carried out by the density functional theory (DFT) calculations. We model the defective diamond of substitutional and interstitial nitrogen atoms by using a simple-cubic supercell. Atoms in the supercell are relaxed by allowing them to move so that the atomic forces are less than 5.0 × 10-3 eV/Å. We calculate the formation energy for substitutional and interstitial sites. We find that the formation energy for the substitutional defect is10.89 eV. We check the convergence of the calculation with respect to the k×k×k - Monkhorst-Pack grids. We show that the energy difference between k = 4 and 6 is very small (7.0 meV). We also check the calculations by using a 216-sites supercell and find that the energy difference is 0.10 eV. Thus, the calculations of the formation energy converge well. As for the interstitial defect, we model some possible configurations and find that the smallest formation energy is 21.88 eV. Therefore, the most stable configuration of the nitrogen-doped diamond belongs to the substitutional site.

A density functional theory study on the structural and electronic properties of PbxSbySez (x + y + z = 2, 3) clusters

2018 ◽  
Vol 32 (03) ◽  
pp. 1850024
Author(s):  
Rengi̇n Peköz ◽  
Şaki̇r Erkoç
Keyword(s):  
Density Functional Theory ◽  
Electronic Properties ◽  
Density Functional ◽  
Ground States ◽  
Density Functional Theory Calculations ◽  
Energy Difference ◽  
Binding Energies ◽  
Functional Theory ◽  
Structural And Electronic Properties ◽  
Scalene Triangle

The structural and electronic properties of neutral ternary PbxSbySez clusters (x + y + z = 2, 3) in their ground states have been explored by means of density functional theory calculations. The geometric structures and binding energies are systematically explored and for the most stable configurations of each cluster type vibrational frequencies, charges on atoms, energy difference between highest occupied and lowest unoccupied molecular orbitals, and the possible dissociations channels have been analyzed. Depending on being binary or ternary cluster and composition, the most energetic structures have singlet, doublet or triplet ground states, and trimers prefer to form isosceles, equilateral or scalene triangle structure.

scholarly journals Density functional theory calculations of merohedric twinning in KLiSO4

2019 ◽  
Vol 234 (4) ◽  
pp. 211-217
Author(s):  
Hans Grimmer ◽  
Bernard Delley
Keyword(s):  
Density Functional Theory ◽  
Aqueous Solutions ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Energy Difference ◽  
Boundary Plane ◽  
Temperature Phase ◽  
Functional Theory ◽  
Transformation Twins ◽  
Polysynthetic Twin

Abstract Density functional theory (DFT) calculations have been performed on five models of periodic, polysynthetic twin interfaces in the ambient-temperature phase of KLiSO4, which has space group P63. The models represent the three merohedric twin laws (m||z, 2⊥z and 1̅) with boundary plane (1 0 1̅ 0), also with boundary plane (0 0 0 1) in case of m, and with boundary plane (1 2̅ 1 0) in case of 1̅. The models satisfy stoichiometry at the boundary plane and maintain the fourfold coordination of the Li and S atoms and the twofold coordination of the oxygen atoms. Relaxed lattice parameters and atomic positions were determined by DFT, using the DMol3 code with functional PBEsol. The energy difference between polysynthetic twin and single crystal per primitive cell of the twin is 0.0009 eV for m(0 0 0 1), 0.09 eV for 1̅(1 0 1̅ 0), 0.58 eV for m(1 0 1̅ 0) and 0.55 eV for 2(1 0 1̅ 0). In KLiSO4 crystals grown from aqueous solutions the first twin was frequently observed, similarly also the second twin in Cr-doped crystals, whereas the third twin appeared only rarely and the fourth was not observed. Not only for KLiSO4 but also for quartz, the energy of twins and the frequency of their occurrence are closely connected for crystals grown from aqueous solutions, whereas for the formation of transformation twins the availability of twin nuclei plays a major role.

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