PRINCIPAL INVESTIGATORS
A systematic study of silicon carbide nanocones, carbon nanocones and silicon nanocones of disclination angles 600 with different tip geometries using the finite cluster approximation is presented. The geometries of the nanocones have been spin optimized using the hybrid functional B3LYP (Becke’s three-parameter exchange functional and the Lee–Yang–Parr correlation functional) and the Lanl2DZ standard basis set as implemented in the Gaussian 03 program (2001). The study indicates that the binding energy per atom or the cohesive energy of the nanocones depends not only on the size of the nanocones but also on the disclination angle of the nanocones. The study also shows that the electronic properties of nanocones depend on disclination angles, size of the nanocone clusters, and the structure of edge of the nanocones. A study of binding energies, the gap between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), height, dipole moment (D.M), charge distribution and density of states (DOS) has been performed for all nanocones under study.
Hybrid density functional theory has been used to study the electronic and geometric structure properties of silicon-carbide nanoclusters containing up to ten atoms. The hybrid functional used is Becke’s three-parameter exchange functional with the exchange-correlation functional of Lee, Yang, and Parr (B3LYP). An all electron 6-311G basis set as implemented in the suite of software Gaussian 03 has been used for accurate determinations of all properties of the SimCn (m + n ≤ 10) nanoclusters and complete geometry optimizations of different possible structures for a specific cluster have been carried out. One of the primary goals of this work is to determine how the structures, bonding and relative stabilities of the clusters are affected by size and stoichiometry. Detailed results are presented on the isomeric energy level differences, electronic state, binding energy per atom, HOMO-LUMO gap, vertical ionization potential, vertical electron affinity, fragmentation energies and Mulliken atomic charges. The stability of the cluster varies with the ratio of the number of silicon to carbon atoms in the cluster. Clusters with greater numbers of carbon atoms are found to be particularly stable. In particular, Si2C5 cluster was found to be a candidate for a highly stable or a so-called “magic cluster”. Overall, carbon-rich aggregates prefer linear or planar geometries and silicon rich aggregates prefer 3D geometries. Results have been compared with other experimental and theoretical results available in the literature.
A systematic study of silicon carbide nanocones, carbon nanocones and silicon nanocones of disclination angles 120o with different tip geometries using the finite cluster approximation is presented. The geometries of the nanocones have been spin optimized using the hybrid functional B3LYP (Becke’s three-parameter exchange functional and the Lee–Yang–Parr correlation functional) and the Lanl2DZ standard basis set as implemented in the Gaussian 03 program (2001). The study indicates that the binding energy per atom or the cohesive energy of the nanocones depends not only on the size of the nanocones but also on the disclination angle of the nanocones. The study also shows that the electronic properties of nanocones depend on disclination angles, size of the nanocone clusters, and the structure of edge of the nanocones. A study of binding energies, the gap between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), height, dipole moment (D.M), charge distribution and density of states (DOS) has been performed for all nanocones under study.
Mechanochemistry deals with the behavior of molecules under an applied stress. Constrained Geometries Simulate External Forces (COGEF) is one of the method used to study the mechanochemistry. In this method, the molecule is first optimized, then the distance between the selected freezed atoms is increased in a stepwise fashion and the molecule’s energy is found after each step. Applied force is calculated by dividing the energy difference between first optimized state and distorted state by step size. A hybrid density functional B3LYP along with pseudopotential basis set LanL2DZ as implemented in Gaussian-09 suites of program is used to find the energy. In this work, we studied and compared the mechanochemistry of SiCNT and CNT. We calculated their Young's modulus and compared their respective force-extension curves.
Silicon Carbide nanocones has good mechanical properties and are used in detection of toxic gases. Most of toxic gases are colorless, odorless and tasteless. It is not easy to have timely alertness to their presence. Study of interaction of toxic gases CO, NO, etc. with silicon carbide nanocone tips might help develop detection and removal techniques for these toxic gases upto the precision of single molecule. A systematic study of SiC nanocones of disclination angle 240o and pentagonal tip geometry using finite cluster approximation is presented. Following optimization with Density functional theory approach, B.E. per atom, HOMO-LUMO gap, bond length, electron transfer and orbital change were calculated. Changes in B.E. per atom, HOMO-LUMO gap, bond length, electron transfer and orbital etc. help in determination of interaction of a toxic gas with nanocone. Electronic properties of SiC nanocones and toxic gases were studied and comparedctive force-extension curves.
Photochromism is the property of a molecule to undergo a light induced reversible change of color based on a chemical reaction. In trans-cis isomerization, trans-isomer undergoes light induced cyclization reaction to form a cis-isomer. Density Functional Theory (DFT) with the 6-311G(2d,2p) basis set and an exchange correlation functional B3LYP, CAM-B3LYP and M06 are implemented in the Gaussian09 software. It is used to find the ground state energy, HOMO-LUMO gap, binding energy per atom, etc. of trans and cis forms of different diarylethene molecules.The frequency of light which induces trans to cis form conversion of these molecules is calculated.Besides, TD-DFT is used also to find the UV-VIS spectrum and the energy and frequency of light.
In the present work, we have carried out First-Principles calculations to study electronic , total density of states and band structures of SiC polytypes. All these calculations were based on Density Functional Theory (DFT) along with Pseudopotentials approach within Generalized Gradient Approximation (GGA). We have used Quantum ESPRESSO (QE) software package for the computational. We have calculated cubic unit cell and hexagonal unit cell of SiC polytypes such as 2H, 3C,4H, 5H, 6H, 8H and 16H with ibrav = 1 for cubic and ibrav = 4 for hexagonal for our calculation. Optimization of the cif structure of SiC polytypes to obtain the ground state energy of the systems. After the optimization of the structure, 3C-SiC polytype has more stable than other polytypes which we are taken. Our further calculations density of states and electronic band structures shows that 3C-SiC has more semiconductor than other polytypes of SiC and its band gap is found to be 1.2 eV which close agreement with standard values.
We report the results of our first principle study based on density functional theory on the interaction of base pair molecules Adenine (A), Cytosine (C), Guanine (G), Thymine (T), and Uracil (U) with the Silicon Carbide Nanocone of disclination angle 240o. Change in HOMO-LUMO gap, binding energy per atom, bond length, electron transfer etc help in determination of interaction of a base pair with nanocone. A hybride density functional B3LYP along with basis set 3-21G∗ as implemented in Gaussian 09 program is used for ground state energy of the nanocones under study. The study also shows that the binding energy per atom of nanocones depend on the size of the nanocone. Binding energy per atom of nanocone is decreasing for the interaction with base pair. Nanocone can be interacted with base pairs. Electronic properties of SiC nanocones and base pairs were studied and determined. A study of binding energy, HOMO-LUMO gap, dipole moment, charges distribution, bond length has been performed for nanocones under study.
Hybrid density functional theory has been used to study the electronic, geometric structure and vibrational properties of silicon-carbide nanoclusters containing up to ten atoms. DFT with the 6-311G (2d,2p) basis set and exchange correlation functional B3LYP is implemennted in the Gaussian 09 software which has been used for determination of normal mode of vibration, frequency, infrared and IR spectrum of SimCn nanoclusters. Furthermore, HOMO-LUMO gap, dipole moment and Mulliken atomic charges of silicon carbide nanocluster were also calculated. Here, we found that with the increasing number of atoms the mode of vibration is also increased. We also observed that the greater the change in dipole moment the larger the peak will be observed in the spectrum.
