Generalization of Baur's correlations between bond length and bond strength in inorganic structures

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Sodium ammonium hydrogen phosphate tetrahydrate (NaNH4HPO4.4H20, stercorite) crystallizes in the space group P1 with a= 10.636 (2), b=6.9187 (14), c=6.4359 (13) ,&, c¢=90.46 (3), fl=97.87 (3), y= 109.20 (3) °, Z= 2. The structure was solved by direct methods and refined anisotropically (R = 0.087) with 1582 reflexions collected from a twinned crystal on a diffractometer (Cu K~t radiation). Corrections for absorption and anomalous scattering were applied. C2/m pseudo-symmetry, which accounts for easy {010} twinning, is obeyed by nearly the whole structure with the exception of the two positions occupied by a water molecule and NH + respectively. A (100) layered structure is built up by [010] rows of Na octahedra sandwiched between P tetrahedra; NH + and its pseudo-equivalent water molecule, which have tetrahedral environments, intercalate the layers and link them through hydrogen bonds. The bond strengths and the geometry of the tetrahedral anion are discussed.

Section: Bond Strengths and Coordination Pol)hedrasupporting

confidence: 72%

“…Possibly because of the low accuracy of the experimental data, attempts to introduce the usual (see Catti & Ferraris, 1973) Table 1 with the significant figures of the e.s.d. 's.…”

Section: Distances (~) and Angles (O) Involving The Water Moleculesmentioning

confidence: 99%

Hydrogen bonding in the crystalline state. Crystal structure and twinning of NaNH₄HPO₄.4H₂O (stercorite)

Ferraris¹,

Franchini-Angela²

1974

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“…4(a) (p = -0.63). This correlation can easily be understood qualitatively in terms of a simple electrostatic model of the hydrogen bond or, even, roughly quantitatively, on the basis of empirical bond strengths (Baur, 1970;Brown & Shannon, 1973;Ferraris & Catti, 1973). In fact, the closer the acceptor is to the H atom, the higher the bond strength brought away from the H atom and the longer, consequentially, is the W-H bond.…”

Section: Correlations Between Bond Lengths and Anglesmentioning

confidence: 99%

The water molecule in crystalline hydrates studied by neutron diffraction

Chiari¹,

Ferraris²

1982

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192

A survey of the geometry and environment of water molecules in crystalline hydrates is presented. Histograms and correlation analyses are based on 97 crystal structures accurately determined by neutron diffraction, and include data from 183 water molecules, each donating two hydrogen bonds. The sample is analyzed according to the nature of the hydrogen-bond acceptors and of the coordinated cations. Cases of bifurcated hydrogen bonds are also discussed. The hydrogen bonds tend to be linear and the acceptors tend to be located close to the water plane. The tendency of coordination bonds to be collinear with the direction of one of the lone pairs of the O or their bisector increases with the strength of the bonds.

“…In gypsum, CaSO4.2HzO (Cole & Lancucki, 1974), the S-O distances, 1.457 and 1.461 A, are a little shorter than the present values. Ferraris & Catti (1973) have recently deduced an empirical relationship between predictive length (L) and bond strength (p) of the form:…”

mentioning

confidence: 99%

Anhydrite: a refinement

Morikawa¹,

Minato²,

Tomita³

et al. 1975

Abstract. CaSO4 (Berchtesgaden, Germany): orthorhombic, Bmmb, a = 6"992 (1), b = 6.999 (1), c = 6-240 (1) /~, Z=4, Dx=2"96 g cm -3. Refinement with diffractometer data yielded a final R value of 0.021. The two independent S-O bond lengths are 1.474 (2) and 1.475 (2)/k.Introduction. Intensities were collected from a cubeshaped crystal (edge length about 0.12 mm) with a Rigaku automated four-circle diffractometer and Mo K~ radiation monochromatized by a graphite plate. The co-20 scan technique was employed with a scan speed of 2 ° rain -I in o9. In all, 266 independent reflexion data were obtained within the range 20 < 70 °. Intensities were corrected for Lorentz and polarization