Search results for: Tapas Kar

Items from 1 to 20 out of 52 results

article

Modelowanie właściwosci wiązań wodorowych na przykładzie kompleksów układ amidowy - woda

Kacper Rzepiela, Aneta Buczek, Teobald Kupka, Tapas Kar, more

Wiadomości Chemiczne > 2023 > [Z] 77, 7-8 > 629--645

The energy and structure of intermolecular hydrogen bonds between water molecule and N-methylamide (NMA) or uracil (U) are discussed on the basis of DFT calculations. Theoretical methods are applied to calculate properties of cis- and trans- NMA complexes with one water molecule. Subsequently, H-bonds in six uracil – water complexes are analyzed. The influence of dispersion interactions and the polar...

article

Local aromaticity in polyacenes manifested by individual proton and carbon shieldings: DFT mapping of aromaticity

Magdalena Gajda, Łukasz Gajda, Teobald Kupka, Tapas Kar

Magnetic Resonance in Chemistry > 58 > 2 > 145 - 153

Exponential dependencies between locally calculated geometric and magnetic indexes of aromaticity, harmonic oscillator model of aromaticity (HOMA) and nucleus independent chemical shifts (NICS)(0), NICS(1) and NICS(1)zz, and the number of conjugated benzene rings in linear acenes, from benzene to decacene were observed at B3LYP/6‐311+G** level of theory. Correlations between HOMA and NICS indexes...

article

Theoretical insight into a feasible strategy of capturing, storing and releasing toxic HCN at the surface of doped BN-sheets by charge modulation

Abdolvahab Seif, Alimorad Rashidi, Steve Scheiner, Khaled Azizi, more

Applied Surface Science > 2019 > 496 > C

The response of boron nitride nanosheets (BNNSs), with the chemical composition of B ₂₅ N ₂₅ H ₂₀ , serving as an adsorbent of toxic hydrogen cyanide (HCN) is explored by using density functional theory (M06-2X variant of DFT). Atoms were treated with a triple-zeta quality basis set with p- and d-polarized functions, namely 6-311G(d,p). The primary focus of this study is to explore adsorption properties...

article

Performance of polarization-consistent vs. correlation-consistent basis sets for CCSD(T) prediction of water dimer interaction energy

Teobald Kupka, Aneta Buczek, Małgorzata A. Broda, Adrianna Mnich, more

Journal of Molecular Modeling > 2019 > 25 > 10 > 1-12

Detailed study of Jensen’s polarization-consistent vs. Dunning’s correlation-consistent basis set families performance on the extrapolation of raw and counterpoise-corrected interaction energies of water dimer using coupled cluster with single, double, and perturbative correction for connected triple excitations (CCSD(T)) in the complete basis set (CBS) limit are reported. Both 3-parameter exponential...

article

Evaluation of Lignans from Piper cubeba against Schistosoma mansoni Adult Worms: A Combined Experimental and Theoretical Study

Renato L. T. Parreira, Eveline S. Costa, Vladimir C. G. Heleno, Lizandra G. Magalhães, more

Chemistry & Biodiversity > 16 > 1 > n/a - n/a

Six dibenzylbutyrolactonic lignans ((−)‐hinokinin (1), (−)‐cubebin (2), (−)‐yatein (3), (−)‐5‐methoxyyatein (4), dihydrocubebin (5) and dihydroclusin (6)) were isolated from Piper cubeba seed extract and evaluated against Schistosoma mansoni. All lignans, except 5, were able to separate the adult worm pairs and reduce the egg numbers during 24 h of incubation. Lignans 1, 3 and 4 (containing a lactone...

article

Aluminum doping makes boron nitride nanotubes (BNNTs) an attractive adsorbent of hydrazine (N₂H₄)

Saraswathi Muniyandi, Rajashabala Sundaram, Tapas Kar

Structural Chemistry > 2018 > 29 > 1 > 375-382

Adsorption of toxic hydrazine (N₂H₄) at the surface of pristine and Al-doped single-wall boron nitride nanotubes (BNNTs and Al-BNNTs) has been investigated using density functional theory (DFT). Single hydrazine molecule was allowed to interact with Lewis acid center (i.e., B atom) of BNNTs, where most stable gauche conformer of the guest is used. Both zigzag (8,0) and armchair (4,4) variants of BNNTs...

article

Electronic properties and metal-ligand bonding situation in Eu(III) complexes containing tris(pyrazolyl)borate and phenantroline ligands

Renato L.T. Parreira, Eduardo J. Nassar, Eder H. da Silva, Lucas A. Rocha, more

Journal of Luminescence > 2017 > 182 > C > 137-145

In this paper we report the preparation, characterization (infrared absorption spectroscopy, photoluminescence, and thermogravimetric analysis), and DFT based electronic structure calculations (GKS-EDA), used to shed light into the metal-ligand bonding situation, of a set of Eu³⁺ complexes containing tris-(pyrazolyl)borate “scorpionate” (Tp) and phenantroline (phen) as ligands in different proportions...

article

Segmentation and additive approach: A reliable technique to study noncovalent interactions of large molecules at the surface of single‐wall carbon nanotubes

Ana M. Torres, Steve Scheiner, Ajit K. Roy, Andrés M. Garay‐Tapia, more

Journal of Computational Chemistry > 37 > 21 > 1953 - 1961

This investigation explores a new protocol, named Segmentation and Additive approach (SAA), to study exohedral noncovalent functionalization of single‐walled carbon nanotubes with large molecules, such as polymers and biomolecules, by segmenting the entire system into smaller units to reduce computational cost. A key criterion of the segmentation process is the preservation of the molecular structure...

chapter

Functionalization of Single-Wall Carbon Nanotubes: An Assessment of Computational Methods

Brahim Akdim, Tapas Kar, Xiaofeng Duan, Ruth Pachter

Lecture Notes in Computer Science > Computational Science - ICCS 2004 > Track on Applications > 260-267

We summarize a theoretical study for modeling functionalization of single-wall carbon nanotubes (SWCNTs), specifically first principles density functional theory calculations, as compared to semi-empirical or simplified hierarchical methods. We focus on the assessment of the methods to be applied to obtain reliable results and gain a fundamental understanding of the diazotization and ozonolysis of...

article

Competition between carboxylic and phenolic groups for the preferred sites at the periphery of graphene – A DFT study

Baliram Lone, Steve Scheiner, Tapas Kar

Carbon > 2014 > 80 > C > 405-418

The energetics of placing carboxyl and phenolic groups at the periphery of a graphene sheet are studied using density functional theory (B3LYP) with a 6-31G^∗ basis set, augmented with diffuse functions on oxygen atoms. Individually both COOH and OH have the same preference for the corner sites, but in presence of COOH the smaller OH group opts for its second preference, the zigzag sites, leaving corner...

article

Do phenolic and carboxylic groups coexist at the tips of oxidized single-wall carbon nanotubes (o-SWNTs)?

Upendra Adhikari, Steve Scheiner, Ajit K. Roy, Tapas Kar

Carbon > 2014 > 73 > Complete > 194-205

Vibrational frequency analyses using density functional theory (DFT) resolves some structural features of purified oxidized single-wall carbon nanotubes (o-SWNTs). Both COOH and phenolic OH (OH _ph ) groups, predicted in several experimental studies to be present in o-SWNTs, were considered at the tips of armchair and zigzag tubes with varying diameters. Hydrogen bonding, where carbonyl oxygen...

article

Generalized interatomic pair-potential function

Jianing Colin Xie, Sudhanshu K. Mishra, Tapas Kar, Rui-Hua Xie

Chemical Physics Letters > 2014 > 605-606 > C > 137-146

Based on a three-parameter molecular orbital-type pair-potential function, we have proposed a generalized interatomic pair-potential function. This new function has been demonstrated to be able to describe accurately and adequately the potentials of the metastable diatomic dications (e.g., He2++, BeH⁺⁺, AlH⁺⁺), and the ground states of covalent bonding systems (e.g., H₂, Si₂, HCl, NO, LiH, HeH⁺, and...

article

Improved pair-potential function for diatomic systems

Jianing Colin Xie, Tapas Kar, Sudhanshu K. Mishra, Rui-Hua Xie

Chemical Physics Letters > 2014 > 593 > Complete > 77-82

A three-parameter pair-potential model recently constructed is improved in the short- and long-range interaction regions. We demonstrate that this improved potential function is able to accurately describe the entire potentials of the ground-state van der Waals systems such as rare-gas, triplet H ₂ , Alkali-helium, Alkaline-earth, and group 12 diatomic systems. All these systems show a single...

article

An accurate pair potential function for diatomic systems

Jianing Colin Xie, Tapas Kar, Rui-Hua Xie

Chemical Physics Letters > 2014 > 591 > C > 69-77

Based on the molecular-orbital theory for a simplest single-electron diatomic system, we have developed a unique functional form for pair potentials. We have demonstrated that the diatomic potential thus constructed is able to adequately describe a stable as well as meta-stable diatomic system with a good accuracy for all relevant internuclear distances.

article

IR Characterization of Tip-Functionalized Single-Wall Carbon Nanotubes

Tapas Kar, Steve Scheiner, Soumya S. Patnaik, Holger F. Bettinger, more

The Journal of Physical Chemistry C > 2010 > 114 > 49 > 20955 - 20961

article

Analysis of the Reactivities of Protein C−H Bonds to H Atom Abstraction by OH Radical

Steve Scheiner, Tapas Kar

Journal of the American Chemical Society > 2010 > 132 > 46 > 16450 - 16459

article

AlN, GaN, AlxGa1−xN nanotubes and GaN/AlxGa1−xN nanotube heterojunctions

James M. de Almeida, Tapas Kar, Paulo Piquini

Physics Letters A > 2010 > 374 > 6 > 877-881

Semiconductor optoelectronic devices based on GaN and on InGaN or AlGaN alloys and superlattices can operate in a wide range of wavelengths, from far infrared to near ultraviolet region. The efficiency of these devices could be enhanced by shrinking the size and increasing the density of the semiconductor components. Nanostructured materials are natural candidates to fulfill these requirements. Here...

article

Erratum: Periodicity in proton conduction along a H‐bonded chain. Application to biomolecules

Alexander Isaev, Tapas Kar, Steve Scheiner

International Journal of Quantum Chemistry > 110 > 5 > 1136 - 1136

article

Borazine and Benzene Homo- and Heterodimers

Holger F. Bettinger, Tapas Kar, Elsa Sánchez-García

The Journal of Physical Chemistry A > 2009 > 113 > 14 > 3353 - 3359

article

Theoretical Study of the Effect of Structural Modifications on the Hyperpolarizabilities of Indigo Derivatives

Prasanta K. Nandi, Nabamita Panja, Tapan K. Ghanty, Tapas Kar

The Journal of Physical Chemistry A > 2009 > 113 > 11 > 2623 - 2631

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INFONA - science communication portal

Search results for: Tapas Kar

Modelowanie właściwosci wiązań wodorowych na przykładzie kompleksów układ amidowy - woda

Local aromaticity in polyacenes manifested by individual proton and carbon shieldings: DFT mapping of aromaticity

Theoretical insight into a feasible strategy of capturing, storing and releasing toxic HCN at the surface of doped BN-sheets by charge modulation

Performance of polarization-consistent vs. correlation-consistent basis sets for CCSD(T) prediction of water dimer interaction energy

Evaluation of Lignans from Piper cubeba against Schistosoma mansoni Adult Worms: A Combined Experimental and Theoretical Study

Aluminum doping makes boron nitride nanotubes (BNNTs) an attractive adsorbent of hydrazine (N₂H₄)

Electronic properties and metal-ligand bonding situation in Eu(III) complexes containing tris(pyrazolyl)borate and phenantroline ligands

Segmentation and additive approach: A reliable technique to study noncovalent interactions of large molecules at the surface of single‐wall carbon nanotubes

Functionalization of Single-Wall Carbon Nanotubes: An Assessment of Computational Methods

Competition between carboxylic and phenolic groups for the preferred sites at the periphery of graphene – A DFT study

Do phenolic and carboxylic groups coexist at the tips of oxidized single-wall carbon nanotubes (o-SWNTs)?

Generalized interatomic pair-potential function

Improved pair-potential function for diatomic systems

An accurate pair potential function for diatomic systems

IR Characterization of Tip-Functionalized Single-Wall Carbon Nanotubes

Analysis of the Reactivities of Protein C−H Bonds to H Atom Abstraction by OH Radical

AlN, GaN, AlxGa1−xN nanotubes and GaN/AlxGa1−xN nanotube heterojunctions

Erratum: Periodicity in proton conduction along a H‐bonded chain. Application to biomolecules

Borazine and Benzene Homo- and Heterodimers

Theoretical Study of the Effect of Structural Modifications on the Hyperpolarizabilities of Indigo Derivatives

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