In this work, we report an interesting observation of partial ionic bonding due to charge transfe... more In this work, we report an interesting observation of partial ionic bonding due to charge transfer in homogeneous sodium clusters. The charge transfer causes the electronic charge to accumulate on the surface, and the resulting charges on atoms range between +0.4 to -1.0 |e^- |. We also demonstrate that this disparity among effective charges on atoms is geometry dependent, such that atoms experiencing similar surrounding, have equal effective charge. It is speculated that this phenomenon will occur among other homogeneous clusters as well, and its extent will be defined by the valence electron delocalization.
Spectral signatures in the terahertz (THz) frequency region are mainly due to bulk vibrations of ... more Spectral signatures in the terahertz (THz) frequency region are mainly due to bulk vibrations of the molecules. These resonances are highly sensitive to the relative position of atoms in a molecule as well as the crystal packing arrangement. To understand the variation of THz resonances, THz spectra (2-10 THz) of three structural isomers: 2-, 3-, and 4-cyanobenzaldehyde have been studied. THz spectra obtained from Fourier transform infrared (FTIR) spectrometry of these isomers show that the resonances are distinctly different especially below 5 THz. For understanding the intermolecular interactions due to hydrogen bonds, four molecule cluster simulations of each of the isomers have been carried out using the B3LYP density functional with the 6-31G(d,p) basis set in Gaussian09 software and the compliance constants are obtained. However, to understand the exact reason behind the observed resonances, simulation of each isomer considering the full crystal structure is essential. The crystal structure of each isomer has been determined using X-ray diffraction (XRD) analysis for carrying out crystal structure simulations. Density functional theory (DFT) simulations using CRYSTAL14 software, utilizing the hybrid density functional B3LYP, have been carried out to understand the vibrational modes. The bond lengths and bond angles from the optimized structures are compared with the XRD results in terms of root-mean-square-deviation (RMSD) values. Very low RMSD values confirm the overall accuracy of the results. The simulations are able to predict most of the spectral features exhibited by the isomers. The results show that low frequency modes (<3 THz) are mediated through hydrogen bonds and are dominated by intermolecular vibrations.
... Bhalchandra Pujari,1,2,* Kavita Joshi,1 DG Kanhere,1,2 and SA Blundell3 1Department of Physic... more ... Bhalchandra Pujari,1,2,* Kavita Joshi,1 DG Kanhere,1,2 and SA Blundell3 1Department of Physics, University of Pune, Ganeshkhind, Pune 411 007, India 2Centre for Modelling and Simulations, University of Pune, Ganeshkhind, Pune 411 007, India 3Département de ...
... Prachi Chandrachud,1 Kavita Joshi,2 and DG Kanhere1,2 1Department of Physics, University of P... more ... Prachi Chandrachud,1 Kavita Joshi,2 and DG Kanhere1,2 1Department of Physics, University of Pune, Ganeshkhind, Pune 411 007, India 2Centre for Modeling and Simulation, University of Pune, Ganeshkhind, Pune 411 007, India Received 4 June 2007; revised manuscript ...
... Bhalchandra S. Pujari,1,2,* Kavita Joshi,2 DG Kanhere,1,2 and SA Blundell3 1Department of Phy... more ... Bhalchandra S. Pujari,1,2,* Kavita Joshi,2 DG Kanhere,1,2 and SA Blundell3 1Department of Physics, University of Pune, Ganeshkhind ... A recent study by Ghosal et al.14 has demonstrated the correlation-induced inhomogeneity in the electronic structure of the quantum dots. ...
We calculate precise correlation energies of ground and low-lying excited states in circular para... more We calculate precise correlation energies of ground and low-lying excited states in circular parabolic quantum dots containing N=2-20 electrons by means of a configuration interaction (CI) method with a numerical, mean-field basis set. All excitations are allowed for 2<=N<=7 (full CI), while up to hextuple excitations are included for N=8,9 , and up to pentuple excitations for 10<=N<=20 . The energies are extrapolated to the limit of basis-set completeness and the truncation error due to restricting the number of Slater determinants is monitored. For high electron densities (Wigner-Seitz radius rs&ap;1.7a0* ), the approach achieves errors of order 0.3mHa* for N=3 , a few mHa* for N=6-9 , rising to about 100mHa* for N=20 . A comparison is made with recent quantum Monte Carlo calculations.
In this work, we report an interesting observation of partial ionic bonding due to charge transfe... more In this work, we report an interesting observation of partial ionic bonding due to charge transfer in homogeneous sodium clusters. The charge transfer causes the electronic charge to accumulate on the surface, and the resulting charges on atoms range between +0.4 to -1.0 |e^- |. We also demonstrate that this disparity among effective charges on atoms is geometry dependent, such that atoms experiencing similar surrounding, have equal effective charge. It is speculated that this phenomenon will occur among other homogeneous clusters as well, and its extent will be defined by the valence electron delocalization.
Spectral signatures in the terahertz (THz) frequency region are mainly due to bulk vibrations of ... more Spectral signatures in the terahertz (THz) frequency region are mainly due to bulk vibrations of the molecules. These resonances are highly sensitive to the relative position of atoms in a molecule as well as the crystal packing arrangement. To understand the variation of THz resonances, THz spectra (2-10 THz) of three structural isomers: 2-, 3-, and 4-cyanobenzaldehyde have been studied. THz spectra obtained from Fourier transform infrared (FTIR) spectrometry of these isomers show that the resonances are distinctly different especially below 5 THz. For understanding the intermolecular interactions due to hydrogen bonds, four molecule cluster simulations of each of the isomers have been carried out using the B3LYP density functional with the 6-31G(d,p) basis set in Gaussian09 software and the compliance constants are obtained. However, to understand the exact reason behind the observed resonances, simulation of each isomer considering the full crystal structure is essential. The crystal structure of each isomer has been determined using X-ray diffraction (XRD) analysis for carrying out crystal structure simulations. Density functional theory (DFT) simulations using CRYSTAL14 software, utilizing the hybrid density functional B3LYP, have been carried out to understand the vibrational modes. The bond lengths and bond angles from the optimized structures are compared with the XRD results in terms of root-mean-square-deviation (RMSD) values. Very low RMSD values confirm the overall accuracy of the results. The simulations are able to predict most of the spectral features exhibited by the isomers. The results show that low frequency modes (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;3 THz) are mediated through hydrogen bonds and are dominated by intermolecular vibrations.
... Bhalchandra Pujari,1,2,* Kavita Joshi,1 DG Kanhere,1,2 and SA Blundell3 1Department of Physic... more ... Bhalchandra Pujari,1,2,* Kavita Joshi,1 DG Kanhere,1,2 and SA Blundell3 1Department of Physics, University of Pune, Ganeshkhind, Pune 411 007, India 2Centre for Modelling and Simulations, University of Pune, Ganeshkhind, Pune 411 007, India 3Département de ...
... Prachi Chandrachud,1 Kavita Joshi,2 and DG Kanhere1,2 1Department of Physics, University of P... more ... Prachi Chandrachud,1 Kavita Joshi,2 and DG Kanhere1,2 1Department of Physics, University of Pune, Ganeshkhind, Pune 411 007, India 2Centre for Modeling and Simulation, University of Pune, Ganeshkhind, Pune 411 007, India Received 4 June 2007; revised manuscript ...
... Bhalchandra S. Pujari,1,2,* Kavita Joshi,2 DG Kanhere,1,2 and SA Blundell3 1Department of Phy... more ... Bhalchandra S. Pujari,1,2,* Kavita Joshi,2 DG Kanhere,1,2 and SA Blundell3 1Department of Physics, University of Pune, Ganeshkhind ... A recent study by Ghosal et al.14 has demonstrated the correlation-induced inhomogeneity in the electronic structure of the quantum dots. ...
We calculate precise correlation energies of ground and low-lying excited states in circular para... more We calculate precise correlation energies of ground and low-lying excited states in circular parabolic quantum dots containing N=2-20 electrons by means of a configuration interaction (CI) method with a numerical, mean-field basis set. All excitations are allowed for 2<=N<=7 (full CI), while up to hextuple excitations are included for N=8,9 , and up to pentuple excitations for 10<=N<=20 . The energies are extrapolated to the limit of basis-set completeness and the truncation error due to restricting the number of Slater determinants is monitored. For high electron densities (Wigner-Seitz radius rs&ap;1.7a0* ), the approach achieves errors of order 0.3mHa* for N=3 , a few mHa* for N=6-9 , rising to about 100mHa* for N=20 . A comparison is made with recent quantum Monte Carlo calculations.
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