Dr.Elaprolu Narsimha Rao

Scopus Publications

Time-Domain Terahertz Spectroscopy and Density Functional Theory Studies of Nitro/Nitrogen-Rich Aryl-Tetrazole Derivatives
Damarla Ganesh, Elaprolu Narsimha Rao, Mottamchetty Venkatesh, Kommu Nagarjuna, Ganapathy Vaitheeswaran, Akhila K. Sahoo, Anil K. Chaudhary
ACS Omega, 2020
The paper reports the time-domain THz spectroscopy studies of noncentrosymmetric energetic nitro/nitrogen-rich aryl-tetrazole high-energy molecules. The fingerprint spectra in the THz domain reveal the role of different functional groups attached to position “1” of the tetrazole moiety, which controls the energetic properties. These responses are deliberated through density functional theory (DFT) calculations. The synthesized aryl-tetrazoles exhibit high positive heat of formation (369–744 kJ/mol), high detonation velocities, and pressures (Dv: 7734–8298 m·s–1; Dp: 24–28 GPa) in comparison to the noncentrosymmetric 2,4,6-trinitrotoluene (TNT). These compounds exhibit variation in the refractive indices and absorption between 0.1 and 2.2 THz range. The DFT studies at the molecular and single-crystal level (using plane wave pseudo potential method) endorse in detecting these bands (with ∼1% deviation). The calculated vibrational frequencies and linear optical properties are found to have good agreement with the experimental data in UV–visible and THz regions.
Structure-property correlation studies of alkaline-earth metal - Azides M(N3)2 (M = Sr, Ba)
Bushnagar Adivaiah, Elaprolu Narsimha Rao, G Vaitheeswaran
Journal of Physics Condensed Matter, 2019
Inorganic metal azides M(N3)2 (M = Sr, Ba) and metal nitrates M(NO3)2 (M = Sr, Ba) are interesting materials due to their wide range of industrial usefulness as gas generators, pyrotechnics, photo graphic materials and explosives. In this work, we explore the mechanical, vibrational (infrared (IR), phonon dispersion), Born Effective Charge (BEC) and thermodynamic properties of these materials to understand the sensitivity correlation studies using plane wave pseudopotential method. As these materials are layered with crucial non bonding interactions, the generalized gradient approximation (GGA) with Tkatchenko Scheffler (for Sr(N3)2) and Ortmann- Bechstedt-Schmidt (for Ba(N3)2) dispersion correction methods are adopted to compute accurate ground state properties with norm-conserving pseudopotentials. The calculated lattice parameters, unit cell volumes, bond lengths are well reproduced with 1% deviation when compared to the experimental and previously reported theoretical data. The mechanical (single crystal, poly-crystalline elastic constants) property correlations corroborate with the experimental impact sensitivity trend. The vibrational, phonon dispersion spectra's, BEC's, thermodynamic properties calculated with density functional perturbative theory (DFPT) approach provide better conclusions about the dynamical stability and polarization (optical sensitivity) trends. From the BEC results we propose that M(NO3)2 (M = Sr, Ba) materials may find various optical applications too. Overall, we tried to explain the crucial reasons for the differences in energetic properties of the studied materials.
Structure-Property Correlation Studies of Potassium 4,4′-Bis(dinitromethyl)-3,3′-azofurazanate: A Noncentrosymmetric Primary Explosive
E. Narsimha Rao, G. Vaitheeswaran
Journal of Physical Chemistry C, 2019
The knowledge of mechanical, vibrational, electronic properties, and origin of polarizability of a noncentrosymmetric explosive materials plays a crucial role in understanding the phase transition mechanism and stand-off detection of high energy material (HEM) residues on the surfaces and interfaces. In the present study, we have explored the role of crystal structure and chemical composition in predicting the structural, dynamical, electronic, and optical properties of two newly synthesized noncentrosymmetric green primary explosives, potassium 4,4′-bis(dinitromethyl)-3,3′-azofurazanate (K2BDAF) and potassium 1,1′-dinitramino-5,5′-bistetrazolate (K2DNABT), using density functional theory simulations. The calculated structural and mechanical properties suggest that K2BDAF and K2DNABT are mechanically stable and possess lower bulk modulus values [K2BDAF (18.91 GPa) < K2DNABT (22.4 GPa)] than toxic lead azide Pb(N3)2 (26 GPa). The Born effective charge (BEC) and vibrational, thermodynamic, and phonon disper...
Unusual optical isotropy in anisotropic alkali metal perchlorates MClO 4 (M = Li, Na, K, Rb, Cs)
Prathap Kumar Jharapla, Elaprolu Narsimha Rao, G Vaitheeswaran
Journal of Physics Condensed Matter, 2018
We report a detailed study on structural, vibrational, born effective charge (BEC), electronic and optical properties of the alkali metal perchlorates, MClO 4(M = Li, Na, K, Rb, Cs) based on Density functional theory. The ground state calculations are done using plane wave pseudopotential method by including dispersion corrected method for more accurate prediction of structural and vibrational frequencies. The calculated lattice parameters and bond lengths are consistent with the experimental values. Further, detailed interpretation of the zone centered vibrational modes yields good concurrence between the experimental and calculated values. There is a decrease in wavelength with an increase in frequency (blue shift) from Li → Na → K → Rb → Cs. The obtained BEC shows the mixed covalent-ionic character of the compounds. The electronic and optical properties are calculated using the full potential linearized augmented plane wave method by TB-mBJ potential. The TB-mBJ band structure shows indirect band gap with O-2p states dominating in the valence band. In spite of anisotropic structure, alkali metal perchlorates are found to possess optical isotropy.
Lattice dynamics and thermodynamic properties of alkaline earth metal nitrates M(NO3)2 (M = Sr, Ba): A first principles study
B. Adivaiah, E. Narsimha Rao, T. Atahar Parveen, G. Vaitheeswaran
Journal of Physics and Chemistry of Solids, 2018
Metal nitrates are widely used as oxidizers and in light-producing compositions in both civilian and military explosive applications. In this work we have explored the isomorphous divalent metal nitrates M(NO3)2 (M = Sr, Ba) by using dispersion-corrected density functional theory methods. The equilibrium results calculated with Grimme (G06) (for Sr(NO3)2) and Ortmann-Bechstedt-Schmidt (for Ba(NO3)2) functionals reproduced the experimental lattice parameters. We present the effect of cations on the lattice dynamical properties conjointly with their elastic and thermodynamic properties. The linear response approach within density functional perturbation theory was used to calculate the zone-center vibrational frequencies, phonon dispersion relation, and phonon density of states. The infrared spectrum of these compounds in their fundamental state is studied in the whole 0–1500 cm−1 range, and is critically analyzed in the light of previous experimental investigations. We observed that most of the high-frequency vibrational modes emerge because of the NO3 group. The calculated phonon dispersion curves do not show any vibrational anomaly, confirming the dynamical stability of the compounds in the cubic ( P a 3 ¯ ) phase. The calculated shear anisotropic factors of 1.8 and 2.1 for Sr(NO3)2 and Ba(NO3)2, respectively, indicate that both crystals studied possess considerable mechanical anisotropy. As the thermal behavior of these materials could play a key role in the growth of sustainable smoke compositions, thermodynamic properties such as the entropy, Debye temperature, heat capacity, and enthalpy were calculated. The results reveal that the compounds are thermodynamically stable up to 750 K. This work demonstrates that Sr(NO)2 and Ba(NO3)2 can be reliably used in pyrotechnics as they possess considerable thermal conductivity, leading to a high burn rate. The results presented in this work could open a way to understand the lattice dynamics of materials of this type and could provide necessary input from the pyrotechnic applicability point of view, which would help experimental researchers in the future.
Topological behaviour of ternary non-symmorphic crystals KZnX (X = P, As, Sb) under pressure and strain: A first principles study
Atahar Parveen, E. Narsimha Rao, B. Adivaiah, P. Anees, G. Vaitheeswaran
Physical Chemistry Chemical Physics, 2018
An ab initio study on the impact of hydrostatic pressure and strain on the electronic properties of an unexplored class of ternary Zintl phases KZnX (X = P, As, Sb) is reported.
Role of spin-orbit interaction on the nonlinear optical response of CsPbCO3F using DFT
E. Narsimha Rao, G. Vaitheeswaran, Ali H. Reshak, S. Auluck
Physical Chemistry Chemical Physics, 2017
We explore the effect of spin–orbit interaction (SOI) on the electronic and optical properties of CsPbCO3F using the full potential linear augmented plane wave method with the density functional theory (DFT) approach.
Effect of lead and caesium on the mechanical, vibrational and thermodynamic properties of hexagonal fluorocarbonates: A comparative first principles study
E. Narsimha Rao, G. Vaitheeswaran, A. H. Reshak, S. Auluck
Rsc Advances, 2016
The experimental crystal structure of CsPbCO3F consists of alternate CsF and PbCO3 layers.
Structural, electronic and optical properties of novel carbonate fluorides ABCO3F (A=K, Rb, Cs; B=Ca, Sr)
E. Narsimha Rao, S. Appalakondaiah, N. Yedukondalu, G. Vaitheeswaran
Journal of Solid State Chemistry, 2014
In the present study, we performed first principles calculations on the electronic and optical properties of layered alkali–alkaline earth carbonate fluorides which attract attention in the domain of nonlinear optics. The calculated lattice parameters and volumes with and without inclusion of van der Waals (vdW) correction methods to standard density functional methods were compared with experiments. We observed that vdW interactions are predominant in RbCaCO3F and CsCaCO3F as compared with other computed compounds. The calculated bulk modulus from single crystal elastic constants reveals that these materials are all relatively harder than the KH2PO4 (KDP) crystal. We also found that these materials are wide band gap insulators as obtained from Tran–Blaha modified Becke–Johnson potential. The linear optical properties such as dielectric function, refractive indices, birefringence and absorption spectra are presented. Finally, the calculated birefringence values indicate that these crystals could be promising for producing phase matching in the deep ultra-violet region.

Dr.Elaprolu Narsimha Rao

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Scopus Publications