Comparative studies of density functionals in modelling hydrogen bonding energetics of acrylamide dimers

Lin, Yi-De,Wang, Yi-Siang,Chao, Sheng D. Techno-Press 2017 Coupled systems mechanics Vol.6 No.3

Intermolecular interaction energies and conformer geometries of the hydrogen bonded acrylamide dimers have been studied by using the second-order Møller-Plesset (MP2) perturbation theory and the density functional theory (DFT) with 17 density functionals. Dunning's correlation consistent basis sets (up to aug-cc-pVTZ) have been used to study the basis set effects. The DFT calculated interaction energies are compared to the reference energy data calculated by the MP2 method and the coupled cluster method at the complete basis set (CCSD(T)/CBS) limit in order to determine the relative performance of the studied density functionals. Overall, dispersion-energy-corrected density functionals outperform uncorrected ones. The ${\omega}B97XD$ density functional is particularly effective in terms of both accuracy and computational cost in estimating the reference energy values using small basis sets and is highly recommended for similar calculations for larger systems.

Density Functional Analysis of the Spin Exchange Interactions in VOSb₂O₄

Koo, Hyun-Joo Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.7

The spin exchange parameters of $VOSb_2O_4$ were evaluated by performing energy-mapping analysis based on density functional calculations. The spin exchange interaction between the nearest-neighbor $V^{4+}$ ions is strongly antiferromagnetic while other interactions are negligible. Thus, the magnetic structure of $VOSb_2O_4$ is best described by a spin-1/2 Heisenberg antiferromagnetic chain with no spin frustration.

Selectively strong molecular adsorption on boron nitride monolayer induced by transition metal substrate

Kim, G.,Jung, S.C.,Han, Y.K. Elsevier 2013 Current Applied Physics Vol.13 No.9

We studied adsorption of several molecules (CO, CO<SUB>2</SUB>, H<SUB>2</SUB>O, N<SUB>2</SUB>O, NO, NO<SUB>2</SUB>, and O<SUB>2</SUB>) on hexagonal boron nitride (h-BN) monolayers supported on transition metal (TM) surfaces, using density functional calculations. We observed that all the molecules bind very weakly on the pristine h-BN, with binding energies in the range of 0.02-0.03 eV. Interestingly, however, when h-BN is supported on the TM surface, NO<SUB>2</SUB> and O<SUB>2</SUB> become strongly chemisorbed on h-BN, with binding energies of >1 eV, whereas other molecules still physisorbed, with binding energies of ~0.1 eV at most. The electron transfer from TM to p<SUB>z</SUB> states of h-BN played a substantial role in such strong bindings of NO<SUB>2</SUB> and O<SUB>2</SUB> on h-BN, as these molecules possess unpaired electrons that can interact with p<SUB>z</SUB> states of h-BN. Such selective molecular binding on h-BN/TM originates from the peculiar distribution of the spin-polarized highest occupied and lowest unoccupied molecular orbitals of NO<SUB>2</SUB> and O<SUB>2</SUB>. Strong molecular adsorption and high selectivity would make the h-BN/TM system possible for a variety of applications such as catalysts and gas sensors.

Selectively strong molecular adsorption on boron nitride monolayer induced by transition metal substrate

Gyubong Kim,정성철,한영규 한국물리학회 2013 Current Applied Physics Vol.13 No.9

We studied adsorption of several molecules (CO, CO2, H2O, N2O, NO, NO2, and O2) on hexagonal boronnitride (h-BN) monolayers supported on transition metal (TM) surfaces, using density functional calculations. We observed that all the molecules bind very weakly on the pristine h-BN, with binding energiesin the range of 0.02e0.03 eV. Interestingly, however, when h-BN is supported on the TM surface,NO2 and O2 become strongly chemisorbed on h-BN, with binding energies of >1 eV, whereas othermolecules still physisorbed, with binding energies of w0.1 eV at most. The electron transfer from TM topz states of h-BN played a substantial role in such strong bindings of NO2 and O2 on h-BN, as thesemolecules possess unpaired electrons that can interact with pz states of h-BN. Such selective molecularbinding on h-BN/TM originates from the peculiar distribution of the spin-polarized highest occupied andlowest unoccupied molecular orbitals of NO2 and O2. Strong molecular adsorption and high selectivitywould make the h-BN/TM system possible for a variety of applications such as catalysts and gas sensors.

Electronic Structures and Optical Properties of Spinel ZnCr2O4

Nirpendra Singh,이주열 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.5

The electronic structures and optical properties of zinc chromite, ZnCr2O4, were calculated using the density-functional theory within the local-spin-density approximation (LSDA), the LSDA plus Hubbard-like parameter U, LSDA+U, and the spin-polarized generalized-gradient approximation. ZnCr2O4 was found to be a direct-band-gap semiconductor with an optical band gap of 2.9 eV, with the uppermost valence bands (lowermost conduction bands) having mainly Cr-t2g (Cr-e<SUB>g</SUB>) characteristics. The calculated band gap using LSDA+U showed better agreement with the available experimental data than previous calculations. The optical-conductivity and the reflectivity spectra were also calculated. The calculated reflectivity spectrum exhibited two peaks, one at ~3.5 eV and the other at ~5.8 eV, which were assigned to the electronic interband transitions from the O-2p to the Cr-3d states and from the O-2p derived bands to the Cr eg bands, respectively.

Antiferromagnetic Ground State of a C₆₀-Covered Si(001) Surface

Lee, Ji Young,Cho, Jun-Hyung,Kang, Myung Ho WILEY-VCH Verlag 2009 CHEMPHYSCHEM -WEINHEIM- Vol.10 No.2

<P>Modeling magnetism: The antiferromagnetic ground state of the C<SUB>60</SUB>/Si(001)-c(4×4) surface is predicted by means of density functional theory calculations. Two adjacent dangling bonds (DBs) generated by the adsorption of C<SUB>60</SUB> are antiferromagnetically coupled with each other. This study demonstrates that magnetic Si surfaces can be prepared by engineering single Si DBs with unpaired electrons. <img src='wiley_img/14394235-2009-10-2-CPHC200800605-content.gif' alt='wiley_img/14394235-2009-10-2-CPHC200800605-content'> </P> <B>Graphic Abstract</B> <P>Modeling magnetism: The antiferromagnetic ground state of the C<SUB>60</SUB>/Si(001)-c(4×4) surface is predicted by means of density functional theory calculations. Two adjacent dangling bonds (DBs) generated by the adsorption of C<SUB>60</SUB> are antiferromagnetically coupled with each other. This study demonstrates that magnetic Si surfaces can be prepared by engineering single Si DBs with unpaired electrons. <img src='wiley_img/14394235-2009-10-2-CPHC200800605-content.gif' alt='wiley_img/14394235-2009-10-2-CPHC200800605-content'> </P>

Large Low-energy Oscillator Strength for Eu 4f Electrons of a Rare-earth Zintl Compound: EuIn_2P_2

Nirpendra Singh,이주열 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.3

A newly found Zintl compound EuIn_2P_2 has been investigated within the density-functional theory, and results of a detailed investigation of its electronic structure and related properties are reported. We employed the so-called LSDA+U method (LSDA: local-spin-density approximation) with varying U from 0 eV to 7 eV to take into account the strong on-site Coulomb repulsion between the Eu 4f -electrons and to reproduce the semiconducting energy gap of 3.2 meV experimentally observed by J. Jiang and S. M. Kauzlarich [Chem. Mater. 18, 435 (2006)]. The calculations, however, could not reproduce the energy gap even for the largest U value of 7.0 eV because the experimental gap was not an optical gap, but it was deduced from the temperature dependence of resistivity at 26 − 60 K; thus, the experimental gap was not a real ‘semiconducting’ gap. The calculated optical-conductivity spectrum with U = 7.0 eV could not reproduce the experimental spectrum, while with simple LSDA, the calculated spectrum resembled the experimental one rather successfully. Therefore, it seems that the LSDA+U method is not suitable to correctly simulate the optical properties of this compound. Contrary to the expectation, we found that EuIn_2P_2 had a large oscillator strengths for f ! d transitions in the low-energy range (below 1.5 eV); i.e., the peaks located at ∼0.6 eV and ∼1.1 eV in the experimental spectrum are mainly due to transitions from f -bands to d-bands, in which joint density-of-states effects play a key role. We also found that the magneto-optical Kerr effect was quite large in the EuIn_2P_2 compound.

Electronic and Magneto-Optical Properties of Rare-Earth Orthoferrites RFeO3 (R = Y, Sm, Eu, Gd and Lu)

이주열,Nirpendra Singh,S. Auluck 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.2

Orthorhombic rare-earth orthoferrites are studied using density-functional theory. The electronic, optical and magneto-optical properties are investigated in both ferromagnetic (FM) and anti-ferromagnetic (AFM) phases. Our calculations show that the antiferromagnetic phase is energetically favorable. The calculated complex Kerr rotation of YFeO3 is in good agreement with the experimental data. Our calculations yield a value of the magneto-optical Kerr angle between -0.4 to 0.4 degrees. To see the resemblance between the complex Kerr rotation and complex optical conductivity, we also have calculated the diagonal and the off-diagonal components of the optical-conductivity tensor.

Density Functional Analysis of the Spin Exchange Interactions in VOSb2O4

구현주 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.7

The spin exchange parameters of VOSb2O4 were evaluated by performing energy-mapping analysis based on density functional calculations. The spin exchange interaction between the nearest-neighbor V4+ ions is strongly antiferromagnetic while other interactions are negligible. Thus, the magnetic structure of VOSb2O4 is best described by a spin-1/2 Heisenberg antiferromagnetic chain with no spin frustration.

Linear-response Calculation of the Effective Coulomb Interaction between Closed-shell Localized Electrons: Cu, Zn, and ZnO

이우진,김용성 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.5

A linear-response method based on plane-wave basis density-functional theory to calculate the effective Coulomb interaction (U) between closed-shell localized electrons is suggested and applied to the 3d closed-shell systems (Cu, Zn, and ZnO). Since the closed-shell localized states are far below the Fermi level, a large local perturbation potential (α) projected to the localized states is applied to induce a purposeful density response (Δn). From the α, the perturbation potential cost for the density response onset, by which the Δn begins to be induced, is removed. The main screening channel for the effective Coulomb interaction is the itinerant electrons deoccupied from the perturbed localized states. The Cu, Zn, and ZnO 3d electron binding energies are calculated based on the local density approximation plus U, with the U values being calculated from the linear-response and being found to be in good agreement with the experimental values.