Ab initio calculations on the bonding properties of isonitrile and nitrile ligands

In this paper, the review of recent results of calculations of surface relaxations, energetics, and bonding properties for ABO 3 perovskite (001), (011) and (111) surfaces using mostly a hybrid description of exchange and correlation is presented. Both AO and BO 2-terminations of the nonpolar (001) surface and A , BO , and O terminations of the polar (011) surface, as well as B and AO 3-terminations of the polar (111) surface were considered. On the AO -terminated (001) surface, all upper-layer A atoms relax inwards, while all second layer atoms relax outwards. For the BO 2-terminated (001) surface, in most cases, the largest relaxations are on the second-layer metal atoms. For almost all ABO 3 perovskites, the surface rumpling is much larger for the AO -terminated than for the BO 2-terminated (001) surface, but their surface energies are always quite similar. In contrast, different terminations of the (011) ABO 3 surface lead to very different surface energies for the O -terminated, A -terminated, and BO -terminated (011) surface, respectively. A considerable increase in the Ti – O or Zr – O , respectively, chemical bond covalency near the (011) surface as compared both to the bulk and to the (001) surface in ABO 3 perovskites were predicted. According to the results of ab initio calculations for Nb doped SrTiO 3, Nb is a shallow donor; six nearest O ions are slightly displaced outwards from the Nb ion. The F center in ABO 3 perovskites resembles electron defects in the partially-covalent SiO 2 crystal rather than usual F centers in ionic crystals like MgO and alkali halides. The results of calculations for several perovskite KNb x Ta 1-x O 3 (KTN) solid solutions, as well as hole and electron polarons in ABO 3 perovskites are analyzed.

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The mutual influence of Y···N and H···H interactions in XHY···NCH···HM complexes (X = F, Cl, Br; Y = S, Se; M = Li, Na, BeH, MgH): tuning of the chalcogen bond by dihydrogen bond interaction

Canadian Journal of Chemistry ◽

10.1139/cjc-2016-0052 ◽

2016 ◽

Vol 94 (6) ◽

pp. 567-573

Author(s):

Mehdi D. Esrafili ◽

Soheila Asadollahi ◽

Yousef Dadban Shahamat

Keyword(s):

Ab Initio Calculations ◽

Ab Initio ◽

Binary Systems ◽

Mutual Influence ◽

Ternary Complexes ◽

Coupling Constants ◽

Spin Coupling ◽

Cooperative Effects ◽

Bonding Properties ◽

Spin Spin Coupling

The equilibrium structures, interaction energies, and bonding properties of ternary XHY···NCH···HM complexes are studied by ab initio calculations, where X = F, Cl, Br, Y = S, Se, and M = Li, Na, BeH, MgH. The ab initio calculations are carried out at the MP2/aug-cc-pVTZ level. The results indicate that all optimized Y···N and H···H binding distances in the ternary complexes are smaller than the corresponding values in the binary systems. The calculated cooperative energies (Ecoop) are between −0.20 kcal/mol in BrHS···NCH···HBeH and −3.29 kcal/mol in FHSe···NCH···HNa. For a given Y and M, the estimated Ecoop values increase as X = F > Cl > Br. In addition, the selenium-bonded complexes exibit larger Ecoop values than those of the sulfur-bonded counterparts. The cooperativity between Y···N and H···H interactions is further analyzed by quantum theory of atoms in molecules and natural bond orbital methods. Cooperative effects make an increase in the J(Y–N) and J(H–H) spin–spin coupling constants of the ternary complexes with respect to the binary systems.

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Structural stability, elastic constants, bonding characteristics and thermal properties of zincblende, rocksalt and fluorite phases in copper nitrides: plane-wave pseudo-potential ab initio calculations

Open Physics ◽

10.2478/s11534-010-0063-3 ◽

2011 ◽

Vol 9 (1) ◽

Cited By ~ 9

Author(s):

Nawel Kanoun-Bouayed ◽

Mohammed Kanoun ◽

Souraya Goumri-Said

Keyword(s):

Plane Wave ◽

Ab Initio Calculations ◽

Ab Initio ◽

Elastic Constants ◽

Density Functional ◽

Structural Parameters ◽

Population Analysis ◽

Mulliken Charge ◽

Bonding Properties ◽

Pseudo Potential

AbstractWe report plane-wave pseudo-potential ab initio calculations using density functional theory in order to investigate the structural parameters, elastic constants, bonding properties and polycrystalline parameters of copper nitrides in zincblende, rocksalt and fluorite structures. Total and partial densities of states indicate a metallic character of these copper nitrides. We estimate bond strengths and types of atomic bonds using Mulliken charge density population analysis and by calculating the electronic localized function. These results reveal the coexistence of covalent, ionic, and metallic bonding.

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