Application of an Improved Point-Charge Model To Study the Crystal Hg2F2

Liao, Meng‐Sheng; Zhang, Qianer

doi:10.1006/jssc.1999.8344

Cited by 5 publications

(6 citation statements)

References 24 publications

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“…30 The Madelung potential is evaluated on a point grid in the vicinity of the molecular group and is then simulated by fitted charges at a finite number of surrounding points of the real crystal lattice. 29,[31][32][33] Our aim was to model the electrostatic stabilization in a simpler way, one that would allow us to compare different systems without the need to refer to specific crystal environments. The motivation for doing so was our desire to treat in a consistent way real triatomic units found in crystals, together with hypothetical systems (N3 7-), as well as mono-and diatomic fragment anions.…”

Section: Computational Methodologymentioning

confidence: 99%

Electron-Rich Three-Center Bonding: Role of s,p Interactions across the p-Block

Munzarová

Hoffmann

2002

J. Am. Chem. Soc.

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This paper analyzes the importance of s,p mixing-a necessary addition to the simplest Rundle-Pimentel picture-and periodic and group trends in electron-rich three-center bonding. Our analysis proceeds through a detailed quantum chemical study of the stability of electron-rich three-center bonding in triatomic 22-valence electron anions. To provide interpretations, a perturbational molecular orbital (MO) analysis of s,p mixing is carried out. This analysis of the orbitals and the overlap populations is then tested by density functional calculations for a number of linear trihalides, trichalcogenides, and tripnictides. The most important effect of s,p mixing on the in-line bonding is in destabilization of the 3sigma(g) orbital and is determined by the overlap between the s orbital of the central atom and the p orbital of the terminal atom. Further destabilization arises from the repulsion of p(pi) lone pairs. Both of these antibonding effects increase with increasing negative charge of the system. The stability of isoelectronic X(3) systems thus decreases when moving from right to left in the periodic table. Interesting group trends are discerned; for instance, for the electron-rich tripnictides, the ability to accommodate a hypervalent electron count is the largest in the middle rather at the end of the group. Particularly strong s,p mixing can reverse the bonding/antibonding character of MOs: thus MO 2sigma(u) that is responsible for bonding for trihalides and trichalcogenides is actually antibonding in N(3)(7)(-).

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Section: Computational Methodologymentioning

confidence: 99%

Electron-Rich Three-Center Bonding: Role of s,p Interactions across the p-Block

Munzarová

Hoffmann

2002

J. Am. Chem. Soc.

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“…Their usage is inadvisable, however, as the potential resulting from such charges is inaccurate. 25 All tools for wave function analysis indicate that formal charges tend to largely exaggerate the charge separation in ionic systems.…”

Section: Overview Of Existing Cluster Modelsmentioning

confidence: 99%

“…Mulliken charges 65 are one of the simplest methods to transfer results of a wave function analysis to embedding charges and have been used, e.g., in ref. 25. The drawback of Mulliken charges are (i) the equal partitioning of atomic overlap populations, which is problematic for ionic systems, (ii) the neglect of intra-atomic charge distribution, and (iii) the large basis set dependence which is especially problematic for extended or unbalanced basis sets.…”

Section: Overview Of Existing Cluster Modelsmentioning

confidence: 99%

“…An improved description of the ESP at near distances was achieved by expanding the point charge to a charge distribution or multipoles. 25,27,78,79 Further improvement can be achieved, in principle, by replacing the point charges at the boundary with suitable total ion model potentials (TIMPs) that account also for effects of covalent bonding and cluster/environment orthogonality. 26,28,31,77 The TIMPs have to be adapted to the individual bonding situation, however.…”

Section: Overview Of Existing Cluster Modelsmentioning

confidence: 99%

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Calculation of NMR parameters in ionic solids by an improved self-consistent embedded cluster method

Weber

Günne

2010

Phys. Chem. Chem. Phys.

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A new embedded cluster method (extended embedded ion method = EEIM) for the calculation of NMR properties in non-conducting crystals is presented. It is similar to the Embedded Ion Method (EIM) (ref. 1) in the way of embedding the quantum chemically treated part in an exact, self-consistent Madelung potential, but requires no empirical parameters. The method is put in relation to already existing cluster models which are classified in a brief review. The influence of the cluster boundary and the cluster charge is investigated, which leads to a better understanding of deficiencies in EIM. A recipe for an improved semi-automated cluster setup is proposed which allows the treatment of crystals composed of highly charged ions and covalent networks. EIM and EEIM results for (19)F and (31)P shielding tensors in NaF and in four different magnesium phosphates are compared with experimental values from solid state MAS NMR, some of which are measured here for the first time. The quantum part of the clusters is treated at hybrid DFT level (mPW1PW) with atomic basis sets up to 6-311G(3df,3pd). The improved agreement of EEIM allows new signal assignments for the different P-sites in Mg(2)P(4)O(12), alpha-Mg(2)P(2)O(7) and MgP(4)O(11). Conversion equations of the type sigma = A + Bdelta between calculated absolute magnetic shieldings sigma and the corresponding experimental chemical shifts delta are obtained independently from linear regressions of plots of isotropically averaged sigma versus delta values on 19 (31)P signals of small molecules.

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“…The model has been extended to Hg 2 Cl 2 . 71 Hg-199 MAS NMR spectra were recorded for Hg 2 X 2 (X Cl, SCN, NCO, OAc or CF 3 CO 2 ) and compared with those for the corresponding monomers. Differences observed in shielding and other parameters were ultimately related to the electronic environment about each mercury atom in the dimers being dominated by the Hg^Hg bond.…”

Section: Crystal Structures Have Been Reported For [Zn(h 4 Quina) 2 ]...mentioning

confidence: 99%

9 Zinc, cadmium and mercury

Malito

2000

Annu. Rep. Prog. Chem., Sect. A

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This review highlights the 1999 literature for the zinc triad with emphases on co-ordination and organometallic chemistry. For the purposes of this review, cluster complexes are de¢ned as those which contain at least three transition metal atoms, connected by metal^metal bonds and/or by bridging ligands. Co-ordination chemistryImproved performance and information achieved using natural abundance 67 Zn NMR employing a single crystal have been demonstrated for [Zn(OAc) 2 ]Á2H 2 O. 1 Applicability of 113 Cd NMR to the detection of cadmium nitrate complexes with food biopolymers has been demonstrated under different conditions using leguminous seed globulins as an example. 2 Colorimetric tests for mercury(II) ions have been reviewed 3 as have other analytical methods for mercury compounds, particularly chromatographic techniques. 4Group 15 donor ligands There has been a review of divalent zinc-promoted hydrolysis of the phosphodiester bonds of RNA, based upon model compounds from dinucleoside monophosphate to oligio-and poly-nucleotides, and from the point of view of zinc complex formation. 5 Cadmium(II) and mercury(II) complexes with polyamines, nucleosides and nucleotides have also been reviewed. Comprehensive data for stability constants are given. 6 The trimethylene bisadenine complexes [{(H-Ade) 2 (CH 2 ) 3 } 2 -M 2 Cl 8 (H 2 O) 2 ] (M Zn, Cd or Hg) have been prepared, and the structure determined for the cadmium tetrahydrate complex. 7 EPR and single crystal X-ray data have been reported for the ¢ve-co-ordinate bis(L-alanine) complex, [Zn(O 2 CCH-(NH 3 )CH 3 ) 2 ]. 8

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Application of an Improved Point-Charge Model To Study the Crystal Hg2F2

Cited by 5 publications

References 24 publications

Electron-Rich Three-Center Bonding: Role of s,p Interactions across the p-Block

Electron-Rich Three-Center Bonding: Role of s,p Interactions across the p-Block

Calculation of NMR parameters in ionic solids by an improved self-consistent embedded cluster method

9 Zinc, cadmium and mercury

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