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Interactions between planar Cu phthalocyanine molecules, CuPc, arranged in vertical stacking sequence are studied by first-principles density functional (DF) and semiempirical molecular dynamics (MD) methods. Dependence of electronic structure upon interplanar spacing and staggering angle is analyzed in order to interpret observed electrical conductivity and magnetic coupling behavior of partially oxidized Cu(pc)I. MD predictions of equilibrium structure of dimers and tetramers are in excellent agreement with experiment on the linear chain species. DF predictions of interaction energy of dimers are compared with MD and experiment.

Density functional (DF) theory is used to study confined two-dimensional molecular fluids. The approximate DF used here is based upon a functional Taylor series expansion of the excess grand potential about the density of a uniform molecular liquid. This formalism is applied to obtain the density profiles of the hard-ellipse fluid confined between two parallel hard walls. The required direct correlation function is obtained using Percus–Yevick and hypernetted chain approximations for low- and high-number density, respectively. Both the restricted orientation model and the extension of this model are used. Generally, we obtained that the number density of the hard ellipses with the major axes parallel to the wall is larger near the walls than the other directions. To check the results, we show that for isotropic hard-ellipse fluids the average number density in the middle of the wall is almost equal to the bulk density and as we expect the average number density of the ellipses at the wall is nearly equal to the amount of the reduced pressure, βP. We also perform Monte Carlo simulation and find reasonable agreement with our results.

When hadron-quark continuity is formulated in terms of a topology change at a density higher than twice the nuclear matter density $(n_0)$, the core of massive compact stars can be described in terms of quasiparticles of fractional baryon charges, behaving neither like pure baryons nor like deconfined quarks. Hidden symmetries, both local gauge and pseudo-conformal (or broken scale), emerge and give rise both to the long-standing “effective $g_A^{\ast }\approx 1$” in nuclear Gamow–Teller (GT) transitions at $\lesssim n_0$ and to the pseudo-conformal sound velocity $v_{\mathrm{\text{pcs}}}^2/c^2\approx 1/3$ at $\gtrsim 3n_0$. It is suggested that what has been referred to, since a long time, as “quenched $g_A$” in light nuclei reflects what leads to the dilaton-limit $g_A^{\mathrm{\text{DL}}}=1$ at near the (putative) infrared fixed point of scale invariance. These properties are confronted with the recent observations in GT transitions and in astrophysical observations.

The density profiles of a hard Gaussian overlap (HGO) fluid confined in between hard walls and in contact with a hard wall are studied using the density functional theory. The hyper-netted chain (HNC) approximation is used to find the coupled integral equations for the density profiles. The restricted orientation model (ROM) is used. The required homogeneous direct correlation function (DCF) is obtained by solving Ornstein–Zernike (OZ) integral equation numerically, using the Precus–Yevick (PY) approximation and the procedure mentioned by Letz and Latz [Phys. Rev.E60, 5865 (1999)]. We also obtained the DCF of hard ellipsoidal (HE) fluid by using the modified closest approach introduced by Rickayzen [Mol. Phys.68, 903 (1989)]. For both HGO and HE, we calculate the density profiles of molecules parallel and perpendicular to the walls and we compare the results. The calculations are performed for various values of packing fractions of the fluid and various molecular elongations. For moderate elongations, k≤3, the results for HGO and HE are almost the same, especially for the density profile of the molecules parallel to the walls but for k=5 there are some discrepancies between the results, in particular for the density profiles of the molecules perpendicular to the walls.

Adsorbed films of liquid ⁴He are analized, in the framework of Density functionals Theories (DF). In these systems, when the substrate becomes increasingly attractive, the thin films of ⁴He approaches the quasi-bidimensional limit. We study this strongly attractive substrate regime with two DF, the Orsay-Trento (OT) and a recent Hybrid proposal (Hyb), focusing in the energy behavior. It is showed that OT does not reproduce the correct limiting energy curve, and it implies that this functional could not provide reliable results for very strongly attractive substrates like Graphite (Gr). In other hand, with the Hyb DF, the correct energy behavior is found for the adsorption energy of ⁴He on Gr. These results show that OT should not be applied to quasi 2D (confinement) situations, and that Hyb DF provides a much more realistic description.

The density functional theory for the freezing hard spheres is studied. We use a variety of the hard sphere direct correlation functions (DCFs) such as the one introduced by Roth et al. [J. Phys. Condens. Matter14, 12063 (2002)]; we call it RELK DCF, a new hard sphere DCF developed here by a combination of the RELK and the Percus–Yevick DCFs, and finally the generalized mean spherical approximation (GMSA). The structure factor, the freezing, and order parameters are calculated using these DCFs. The structure factor obtained by the new DCF is in good agreement with the Monte Carlo simulation. The best result for the freezing parameters in comparison with the Monte Carlo simulations is obtained by using our new expression for the DCF. Finally we obtain the Helmholtz free energy of the hard sphere FCC crystals using modified weighted density approximation (MWDA), and again the best results are obtained by using the new expression for the hard sphere DCF.

The geometric and electronic structures of the ethylene oxide (EO) molecule adsorbed on Si(100)-$(2\times 1)$ surface were investigated by using the density-functional theory calculations. All possible adsorbed structures were considered and it was found that only four adsorption structures are stable. The calculations of the formation energy revealed the most stable conformation and demonstrated that the nature of Si–O bond significantly affects the stability of adsorption systems. The analysis of corresponding electronic structures showed that two adsorbed structures are still semiconductor compounds but the other two are not. In particular, the EO after adsorbing was found to be connected via a ring-opening reaction where the molecule forms a five-membered ring together with the surface of dimer silicon atoms, and the produced five-membered ring is almost perpendicular to the silicon surface.

Within the density functional theory, the Hartree–Fock/Kohn–Sham-coupled perturbation method using the basis of localized orbitals, the gradient PBE functional with dispersion correction D3(BJ) and hybrid PBE0 and B3LYP functionals, the structural, dielectric, and piezoelectric properties of hexagonal alkali fluorocarbonates ABCO₃F (A: K, Rb, Cs; B: alkaline earth (Mg, Ca, Sr) and $d^{10}$ (Zn, Cd, Pb)) were evaluated. In the series of crystals, fluorocarbonates with lead have the highest values of the calculated components of the dielectric constant tensor, piezoelectric constants, and nonlinear optical (NLO) coefficients.

The stability and electronic structure of a single monatomic Al wire has been studied using the ab initio pseudopotential method. The Al wire undergoes two structural rearrangements under compression, i.e., zigzag configurations at angles of 140° and 60°. The evolution of electronic structures of the Al chain as a function of structural phase transition has been investigated. The relationship between electronic structure and geometric stability is also discussed. The 2p bands in the Al nanowire are shown to play a critical role in its stability. The effects of density functionals (GGA and LDA) on cohesive energy and bond length of Al nanostructures (dimer, chains, and monolayers) are also examined. The link between low dimensional 0D structure (dimer) to high dimensional 3D bulk Al is estimated. An example of optimized tip-suspended finite atomic chain is presented to bridge the gap between hypothetical infinite chains and experimental finite chains.

Molecular dynamics, density functional with correlation, as well as docking studies of inhibitors of HIV-1 reverse transcriptase (RT) are reported. We propose in this work a novel potential HIV-1 RT inhibitor (RTI), which theoretically appears to bind in a similar mode as other nucleoside reverse transcriptase inhibitors, and in addition, it introduces a new hydrogen bond interaction with Trp229. Our novel RTI has high docking scores and the molecular dynamics studies, as well as the analysis of the ligand-receptor interactions in the active site and the ADMET properties suggest advantages and specificities for this potential RTI.

In this paper we report the state of the art CCSD(T)//MP2 ab initio calculations for the activation of propane by cyclopentadienyl carbonyl rhodium, (Cp)Rh(CO), using the effective core potential of Hay and Wadt (LANL2DZ) for rhodium atom and the correlated consistent polarized valence double-ξ basis set (cc-pVDZ) for C, H and O atoms. The CCSD(T) energy values are used as reference to assess the effect of electron correlation on the reaction energies, as well as the performance of density functional theory (DFT) energy values using various functionals. An investigation on the accuracy of DFT results is relevant since their use in calculations involving large molecular systems is a computationally efficient strategy that enables us to tackle important problems in organometallics field and supramolecular chemistry. Our results for the small model system show that all DFT functionals used here correctly predict the CCSD(T) energy pattern and also reproduce very satisfactorily the MP2 geometrical parameters. The BP86, PBE1PBE and PW91 functionals exhibited the best agreement with structural parameters and relative energy values as compared with ab initio post-Hartree–Fock results, showing a potential use in theoretical investigations on larger systems.

The fulerine-Ni@Ge₁₂H₁₂ structure, which composes of four pentagons and four rhombi and is like a fullerene, has a closed-shell electronic structure, the largest HOMO–LUMO energy gap, the highest vertical ionization potential, and the lowest vertical electron affinity. All of these properties are characteristic of a magic cluster, therefore, we strongly suggest fulerine-Ni@Ge₁₂H₁₂ should be a magic cluster and promising as building blocks in developing cluster-assembled nanomaterials. This can be interpreted by the weak interaction between Ni and the cage together with the transference of two electrons from the 4s orbital to the 3d orbital of Ni. The magnetic moment of fulerine-M@Ge₁₂H₁₂(M=Sc–Ni) varies from 0 to 3 μ_B, implying they have potential applications in developing new nanomaterials with tunable magnetic properties. The calculated TDDFT optical properties of fulerine-M@Ge₁₂H₁₂(M=Sc–Ni) can be tuned broadly in the ultraviolet–visible region. This is very important for optoelectronic applications.

Adsorbed films of liquid ⁴He are analized, in the framework of Density Functional Theories (DF). In these systems, when the substrate becomes increasingly attractive, the thin films of ⁴He approaches the quasi-bidimensional limit. We study this strongly attractive substrate regime with two DF, the Orsay-Trento (OT) and a recent Hybrid proposal (Hyb), focusing in the energy behavior. It is showed that OT does not reproduce the correct limiting energy curve, and it implies that this functional could not provide reliable results for very strongly attractive substrates like Graphite (Gr). In other hand, with the Hyb DF, the correct energy behavior is found for the adsorption energy of ⁴He on Gr. These results show that OT should not be applied to quasi 2D (confinement) situations, and that Hyb DF provides a much more realistic description.