SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY

The azocalix[4]arenes molecules such as methylphenylazocalix[4]aren (MPcalix[4]) and methoxyphenylazocalix[4]aren (MOPcalix[4]) have been synthesized and characterized by experimental FT-IR and H-1 NMR spectral analyses. The fundamental vibrational transitions have been addressed by experimental FF-IR (4000-400 cm(-1)) technique and density functional theory (DFT) employing B3LYP level with the 6-31G(d) and 6-311G(d,p) basis sets. The H-1 NMR spectra of the studied compounds have been recorded in chloroform, and compared with computed data obtained by using gauge including atomic orbital (GIAO) method. Furthermore, thermodynamic properties (heat capacity, entropy, and enthalpy changes) and frontier molecular orbitals of the molecules in the ground state have been Calculated by using the same method and basis sets. The non-linear optical properties such as the first order hyperpolarizability (beta(o)), related properties (alpha(0) and Delta(alpha)) are also computed. Information about the charge density distribution of the molecules and its chemical reactivity has been studied by mapping molecular electrostatic potential surface (MEPs). The scaled vibrational frequency values have been compared with experimental FT-IR spectroscopic data. The correlations between the observed and calculated frequencies are in good agreement with each other as well as the correlation of NMR data. The linear polarizability and first hyperpolarizability of the studied molecules indicate that the compounds are a good candidate of nonlinear optical materials. (C) 2015 Elsevier B.V. All rights reserved

spherical Al@Ni and Ni@Al core-shell nanoparticles

Atomic-scale comprehension of structure and thermodynamic stability of metallic core-shell nanoparticles is important for viewpoints of both their synthesis and applications. Thermodynamic and structural properties of Al@Ni and Ni@Al core-shell nanoparticles are investigated at various temperatures by using molecular dynamics (MD) simulations within the interactions defined by the many-body embedded atom model (EAM). The sizes of Al@Ni core-shell nanoparticles and their pure counterparts are chosen as two different values of about 5 nm and 10 nm in this study. MD method is used to calculate the total energy, one-body particle density, radial distribution function, and heat capacity to estimate the melting temperatures of the core-shell systems considered in the present study. Our estimated melting temperatures of core-shell nanoparticles are also verified by doing common neighbor analysis (CNA). MD study shows that a distinct two-stage melting takes place during the heating of the Al@Ni core-shell nanoparticles, although their melting mechanism has started from surface into interior. It is reported that the width of the melting temperature of the core-shell nanoparticles is dependent not only on the bulk melting points of their pure metals but also on the ratio of the shell thickness and the core size of the nanoparticles.The evolution of Al3@Ni3 core-shell nanoparticles during heating process at elevated temperatures (Al atoms are colored in magenta while Ni atoms are in blue).C1 [Kart, S. Ozdemir] Pamukkale Univ, Dept Phys, Kinikli Campus, TR-20017 Denizli, Turkey.[Kart, H. H.] Adnan Menderes Univ, Dept Phys, Cent Campus, TR-09010 Aydin, Turkey.[Cagin, T.] Texas A&M Univ, Dept Mat Sci & Engn, 209 Reed McDonald Bldg, College Stn, TX 77843 USA

dithiophosphate

O,O'-dibornyl dithiophosphate has been synthesized by the reaction of P2S5 and borneol in toluene. Fourier Transform Infrared spectra (FT-IR) of the title compound are measured. The molecular geometry, vibrational frequencies, infrared intensities and NMR spectrum of the title compound in the ground state have been calculated by using the density functional theory (DFT) and ab initio Hartree-Fock (HF) methods with the basis set of 6-31G(d). The computed bond lengths and bond angles show the good agreement with the experimental data. Moreover, the vibrational frequencies are calculated and the scaled values have been compared with experimental FT-IR spectra. Assignments of the vibrational modes are made on the basis of total energy distribution (TED) calculated with scaled quantum mechanical (SQM) method. The observed and calculated FT-IR and NMR spectra are in good agreement with each other. (C) 2014 Elsevier B.V. All rights reserved

Physical properties of Cu nanoparticles: A molecular dynamics study

Thermodynamical, structural and dynamical properties of Cu nanoparticles are investigated by using Molecular Dynamics (MD) simulations at various temperatures. In this work, MD simulations of the Cu-nanoparticles are performed by means of the MPiSiM codes by utilizing from Quantum Sutton-Chen (Q-SC) many-body force potential to define the interactions between the Cu atoms. The diameters of the copper nanoparticles are varied from 2 nm to 10 nm. MD simulations of Cu nanoparticles are carried out at low and high temperatures to study solid and liquid properties of Cu nanoparticles. Simulation results such as melting point, radial distribution function are compared with the available experimental bulk results. Radial distribution function, mean square displacement, diffusion coefficient, Lindemann index and Honeycutt-Andersen index are also calculated for estimating the melting point of the Copper nanoparticles. (C) 2014 Elsevier B.V. All rights reserved

and mechanical properties in the tetragonal rutile phase

Structural and mechanical properties in rutile (tetragonal) phases of SnO2 and TiO2 are investigated by performing first-principle density functional theory (DFT) calculations. Generalized Gradient Approximation (GGA) potentials of electronic exchange and correlation part parameterized by Perdew-Burke-Ernzerhof (PBE) are used. Second order elastic stiffness constants, bulk modulus, First derivative of bulk modulus, and pressure behavior of these mechanical properties are studied up to pressure of 10 GPa. Structural properties and elastic constants of SnO2 and TiO2 calculated in this study are compatible with experimental and other available theoretical studies. Electronic band gap energies of these semiconductors are also calculated. As expected, the calculated values by standard DFT calculations are underestimated in comparison to experimental values. (C) 2014 Elsevier Ltd. All rights reserved

O2-AT-SNO2; PHONONS

The structural properties of SnO2 polymorphs in the sequential order of observed phases in experiments are determined by the density functional theory (DFT) calculations based on local density approximation (LDA) of ultra soft pseudo potentials (US-PPs). Phonon dispersion relations are calculated by the lattice dynamics calculations. Shifts in the infrared (IR) active optical modes due to polarization (LO/TO splitting) are also calculated. Moreover, softening of B-1g mode at the rutile-CaCl2 second-order ferroelastic phase transition is confirmed. Thermal properties, such as temperature behavior of bulk modulus and thermal expansion in the rutile phase are obtained by employing quasiharmonic approximation (QHA). They are in good agreement with the available experimental results. Dynamic stabilities of SnO2 polymorphs except for the rutile phase are checked for the first time by using phonon dispersions. The rutile, CaCl2, pyrite, ZrO2 and cotunnite type structures have shown thermodynamical stability. The cause of alpha-PbO2 phase showing nearly stability is discussed in the light of experimental studies. However, the fluorite type structure is definitely instable even at different pressures. It may not be one of SnO2 polymorphs. (C) 2015 Elsevier B.V. All rights reserved