Unusual 180 degrees P-O-P Bond Angles in ZrP(2)O(7)

The structure of cubic ZrP(2)O(7) at room temperature has been solved and refined using a combination of modeling and high-resolution neutron powder diffraction data. The cell edge is 24.74 ?, the space group is Pa&thremacr;, and Z is 108. For those P(2)O(7) units not on a 3-fold axis, the P-O-P angles range from 134 degrees to 162 degrees. Two crystallographically distinct P(2)O(7) groups are on three fold axes with P-O-P angles thus constrained to be 180 degrees on average. The structure of cubic ZrP(2)O(7) was also refined from data taken at 227, 290, 371, 435, and 610 degrees C. The 3 x 3 x 3 superstructure present at room temperature disappears at about 290 degrees C, and all P-O-P angles of P(2)O(7) are then constrained by symmetry to be 180 degrees on average. The exceptionally low thermal expansion shown by ZrP(2)O(7) above 290 degrees C is likely related to the unusual P-O-P angle.     

Triclinic-cubic phase transition and negative expansion in the actinide IV (Th, U, Np, Pu) diphosphates

The AnP(2)O(7) diphosphates (An = Th, U, Np, Pu) have been synthesized by various routes depending on the stability of the An(IV) cation and its suitability for the unusual octahedral environment. Synchrotron and X-ray diffraction, thermal analysis, Raman spectroscopy, and (31)P nuclear magnetic resonance reveal them as a new family of diphosphates which probably includes the recently studied CeP(2)O(7). Although they adopt at high temperature the same cubic archetypal cell as the other known MP(2)O(7) diphosphates, they differ by a very faint triclinic distortion at room temperature that results from an ordering of the P(2)O(7) units, as shown using high-resolution synchrotron diffraction for UP(2)O(7). The uncommon triclinic-cubic phase transition is first order, and its temperature is very sensitive to the ionic radius of An(IV). The conflicting effects which control the thermal variations of the P-O-P angle are responsible for a strong expansion of the cell followed by a contraction at higher temperature. This inversion of expansion occurs at a temperature significantly higher than the phase transition, at variance with the parent compounds with smaller M(IV) cations in which the two phenomena coincide. As shown by various approaches, the P-O(b)-P linkage remains bent in the cubic form.     

Crystal and molecular structures of alkali oxalates: first proof of a staggered oxalate anion in the solid state

The molecular and crystal structures of solvent-free potassium, rubidium, and cesium oxalates have been determined ab initio from high-resolution synchrotron and X-ray laboratory powder patterns. In the case of potassium oxalate K(2)C(2)O(4) (a = 10.91176(7) A, b = 6.11592(4) A, c = 3.44003(2) A, orthorhombic, Pbam, Z = 2), the oxalate anion is planar, whereas in cesium oxalate Cs(2)C(2)O(4) (a = 6.62146(5) A, b = 11.00379(9) A, c = 8.61253(7) A, beta = 97.1388(4) degrees, monoclinic, P2(1)/c, Z = 4) it exhibits a staggered conformation. For rubidium oxalate at room temperature, two polymorphs exist, one (beta-Rb(2)C(2)O(4)) isotypic to potassium oxalate (a = 11.28797(7) A, b = 6.29475(4) A, c = 3.62210(2) A, orthorhombic, Pbam, Z = 2) and the other (alpha-Rb(2)C(2)O(4)) isotypic to cesium oxalate (a = 6.3276(1) A, b = 10.4548(2) A, c = 8.2174(2) A, beta = 98.016(1) degrees, monoclinic, P2(1)/c, Z = 4). The potassium oxalate structure can be deduced from the AlB(2) type, and the cesium oxalate structure from the Hg(99)As type, respectively. The relation between the two types of crystal structures and the reason for the different conformations of the oxalate anion are discussed.     

Structural chemistry, monoclinic-to-orthorhombic phase transition, and CO2 adsorption behavior of the small pore scandium terephthalate, Sc2(O2CC6H4)CO2)3, and its nitro- and amino-functionalized derivatives

The crystal structure of the small pore scandium terephthalate Sc(2)(O(2)CC(6)H(4)CO(2))(3) (hereafter Sc(2)BDC(3), BDC = 1,4-benzenedicarboxylate) has been investigated as a function of temperature and of functionalization, and its performance as an adsorbent for CO(2) has been examined. The structure of Sc(2)BDC(3) has been followed in vacuo over the temperature range 140 to 523 K by high resolution synchrotron X-ray powder diffraction, revealing a phase change at 225 K from monoclinic C2/c (low temperature) to Fddd (high temperature). The orthorhombic form shows negative thermal expansivity of 2.4 × 10(-5) K(-1): Rietveld analysis shows that this results largely from a decrease in the c axis, which is caused by carboxylate group rotation. (2)H wide-line and MAS NMR of deuterated Sc(2)BDC(3) indicates reorientation of phenyl groups via π flips at temperatures above 298 K. The same framework solid has also been prepared using monofunctionalized terephthalate linkers containing -NH(2) and -NO(2) groups. The structure of Sc(2)(NH(2)-BDC)(3) has been determined by Rietveld analysis of synchrotron powder diffraction at 100 and 298 K and found to be orthorhombic at both temperatures, whereas the structure of Sc(2)(NO(2)-BDC)(3) has been determined by single crystal diffraction at 298 K and Rietveld analysis of synchrotron powder diffraction at 100, 298, 373, and 473 K and is found to be monoclinic at all temperatures. Partial ordering of functional groups is observed in each structure. CO(2) adsorption at 196 and 273 K indicates that whereas Sc(2)BDC(3) has the largest capacity, Sc(2)(NH(2)-BDC)(3) shows the highest uptake at low partial pressure because of strong -NH(2)···CO(2) interactions. Remarkably, Sc(2)(NO(2)-BDC)(3) adsorbs 2.6 mmol CO(2) g(-1) at 196 K (P/P(0) = 0.5), suggesting that the -NO(2) groups are able to rotate to allow CO(2) molecules to diffuse along the narrow channels.     

High-temperature, high-pressure hydrothermal synthesis, crystal structure, and solid-state NMR spectroscopy of Cs2(UO2)(Si2O6) and variable-temperature powder X-ray diffraction study of the hydrate phase Cs2(UO2)(Si2O6) x 0.5H2O

A new uranium(VI) silicate, Cs2(UO2)(Si2O6), has been synthesized by a high-temperature, high-pressure hydrothermal method and characterized by single-crystal X-ray diffraction and solid-state NMR spectroscopy. It crystallizes in the orthorhombic space group Ibca (No. 73) with a = 15.137(1) A, b = 15.295(1) A, c = 16.401(1) A, and Z = 16. Its structure consists of corrugated achter single chains of silicate tetrahedra extending along the c axis linked together via corner-sharing by UO6 tetragonal bipyramids to form a 3-D framework which delimits 8- and 6-ring channels. The Cs+ cations are located in the channels or at sites between channels. The 29Si and 133Cs MAS NMR spectra are consistent with the crystal structure as determined from X-ray diffraction, and the resonances in the spectra are assigned. Variable-temperature in situ powder X-ray diffraction study of the hydrate Cs2(UO2)(Si2O6) x 0.5H2O indicates that the framework structure is stable up to 800 degrees C and transforms to the structure of the title compound at 900 degrees C. A comparison of related uranyl silicate structures is made.     

Properties of chloroformyl peroxynitrate, ClC(O)OONO(2)

The synthesis of ClC(O)OONO(2) is accomplished by photolysis of a mixture of Cl(2), NO(2), and CO in large excess of O(2) at about -70 degrees C. The product is isolated after repeated trap-to-trap condensation. The solid compound melts at -84 degrees C, and the extrapolated boiling point is 80 degrees C. ClC(O)OONO(2) is characterized by IR, Raman, (13)C NMR, and UV spectroscopy. According to the IR matrix spectra, the compound exists at room temperature only as a single conformer. The molecular structure of ClC(O)OONO(2) is determined by gas electron diffraction. The molecule possesses a gauche structure with a dihedral angle of phi(COON) = 86.7(19) degrees , and the C=O bond is oriented syn with respect to the O-O bond. The short O-O bond (1.418(6) A) and the long N-O bond (1.511(8) A) are consistent with the facile dissociation of ClC(O)OONO(2) into the radicals ClC(O)OO and NO(2). The experimental geometry of ClC(O)OONO(2) is reproduced reasonably well by B3LYP/6-311+G(2df) calculations, whereas the MP2 approximation predicts the N-O bond considerably too long and the dihedral angle too small.     

Thermal decomposition of monocalcium aluminate decahydrate (CaAl2O4.10H2O) investigated by in-situ synchrotron X-ray powder diffraction, thermal analysis and 27Al, 2H MAS NMR spectroscopy

The stability of monocalcium aluminate decahydrate, with the nominal composition CaAl(2)O(4).10H(2)O (CAH(10)), has a decisive role for the strength development and durability of cementitious materials based on high alumina cements. This has prompted an investigation of the thermal transformation of crystalline monocalcium aluminate decahydrate in air to an amorphous phase by in-situ synchrotron X-ray powder diffraction in the temperature range from 25 to 500 degrees C, by DTA/TGA, and (2)H, (27)Al MAS NMR spectroscopy. The decomposition includes the loss of hydrogen-bonded water molecules in the temperature range up to 175 degrees C, coupled with a reduction of the unit cell volume from 1928 A(3) at 25 degrees C, to 1674 A(3) at 185 degrees C. Furthermore, X-ray diffraction shows that CaAl(2)O(4).10H(2)O starts to transform to an amorphous phase at approximately 65 degrees C. This phase is fully developed at approximately 175 degrees C and it converts to crystalline CaAl(2)O(4) when heated to 1300 degrees C. The thermal decomposition in the temperature range from approximately 65 to approximately 175 degrees C involves both formation of an amorphous phase including AlO(4) tetrahedra and structural changes in the remaining crystalline phase.     

Tautomeric and conformational properties of malonamide, NH2C(O)-CH2-C(O)NH2: electron diffraction and quantum chemical study

The geometric structure of malonamide, NH2C(O)-CH2-C(O)NH2, has been investigated by gas electron diffraction (GED) and quantum chemical calculations (B3LYP and MP2 approximations with 6-311++G(3df,pd) basis sets). Both GED and quantum chemistry result in the existence of a single diketo conformer in the gas phase. According to GED refinement this conformer possesses (sc,ac) conformation with one C=O bond in synclinal orientation (dihedral angle tau(O=C-C-C)=49.0(3.0) degrees) and the other C=O bond in anticlinal orientation (dihedral angle tau(O=C-C-C)=139.5(3.3) degrees). The experimental geometric parameters are reproduced very closely by the B3LYP method.     

Combined structural refinement of Bi3.5La0.5Ti3O12 using neutron and X-ray powder diffraction data

A combined structural refinement of Bi3.5La0.5Ti3O12 against both neutron and X-ray diffraction data was performed at 298 K on the basis of the Raman study. The upshift of Raman peaks suggested that the substitution sites of La atoms in Bi3.5La0.5Ti3O12 were only the Bi sites in the perovskite units. Of the two crystal structural models (orthorhombic and monoclinic systems) considered for the crystal structural system of Bi3.5La0.5Ti3O12, the weighted R factor, Rwp, and goodness-of-fit indicator, S (=Rwp/Re), of the monoclinic system were lower than those of the orthorhombic one. The final Rwp and S values based on the monoclinic system were 7.04% (6.34 and 7.76% for the neutron data and the X-ray data, respectively) and 1.45, respectively. The lattice parameters obtained from the combined structural refinement were a = 5.4321(1) A, b = 5.4161(1) A, and c = 32.8614(3) A. The beta angle was 89.95(4) degrees . Spontaneous polarizations calculated from the refined structural parameters were 27.0 microC/cm2 for the monoclinic system and 1.8 microC/cm2 for the orthorhombic one.     

Multifunctional lanthanum tetraphosphonates: flexible, ultramicroporous and proton-conducting hybrid frameworks

A new flexible ultramicroporous solid, La(H(5)DTMP)·7H(2)O (1), has been crystallized at room temperature using the tetraphosphonic acid H(8)DTMP, hexamethylenediamine-N,N,N',N'-tetrakis(methylenephosphonic acid). Its crystal structure, solved by synchrotron powder X-ray diffraction, is characterised by a 3D pillared open-framework containing 1D channels filled with water. Upon dehydration, a new related crystalline phase, La(H(5)DTMP) (2) is formed. Partial rehydration of 2 led to La(H(5)DTMP)·2H(2)O (3). These new phases contain highly corrugated layers showing different degrees of conformational flexibility of the long organic chain. The combination of the structural study and the gas adsorption characterization (N(2) and CO(2)) suggests an ultramicroporous flexible framework. NO isotherms are indicative of a strong irreversible adsorption of NO within the pores. Impedance data indicates that 1 is a proton-conductor with a conductivity of 8 × 10(-3) S cm(-1) at 297 K and 98% of relative humidity, and an activation energy of 0.25 eV.     

Two new noncentrosymmetric (NCS) polar oxides: syntheses, characterization, and structure-property relationships in BaMTe2O7 (M = Mg2+ or Zn2+)

Two new noncentrosymmetric (NCS) polar oxides, BaMgTe(2)O(7) and BaZnTe(2)O(7), have been synthesized and characterized, with their crystal structures determined by single crystal X-ray diffraction. The iso-structural materials exhibit structures consisting of layers of corner-shared MgO(5) or ZnO(5), Te(6+)O(6), and Te(4+)O(4) polyhedra that are separated by Ba(2+) cations. The Te(4+) cation is found in a highly asymmetric and polar coordination environment attributable to its stereoactive lone-pair. The alignment of the individual TeO(4) polar polyhedra results in macroscopic polarity for BaMgTe(2)O(7) and BaZnTe(2)O(7). Powder second-harmonic generation (SHG) measurements revealed a moderate SHG efficiency of approximately 5 × KDP (or 200 × α-SiO(2)) for both materials. Piezoelectric charge constants of 70 and 57 pm/V, and pyroelectric coefficients of -18 and -10 μC·m(-2)·K(-1) were obtained for BaMgTe(2)O(7) and BaZnTe(2)O(7), respectively. Although the materials are polar, frequency dependent polarization measurements indicated that the materials are not ferroelectric, that is, the observed macroscopic polarization cannot be reversed. Infrared, UV-vis diffuse spectroscopy, and thermal properties were also measured. Crystal data: BaMgTe(2)O(7), orthorhombic, space group Ama2 (No. 40), a = 5.558(2) ?, b = 15.215(6) ?, c = 7.307(3) ?, V = 617.9(4) ?(3), and Z = 4; BaZnTe(2)O(7), orthorhombic, space group Ama2 (No. 40), a = 5.5498(4) ?, b = 15.3161(11) ?, c = 7.3098(5) ?, V = 621.34(8) ?(3), and Z = 4.     

The stuffed framework structure of SrP2N4: challenges to synthesis and crystal structure determination

SrP2N4 was obtained by high-pressure high-temperature synthesis utilizing the multianvil technique (5 GPa, 1400 degrees C) starting from mixtures of phosphorus(V) nitride and strontium azide. SrP2N4 turned out to be isotypic with BaGa(2)O(4) and is closely related to KGeAlO(4). The crystal structure (SrP2N4, a=17.1029(8), c=8.10318(5) A, space group P6(3) (no. 173), V=2052.70(2) A3, Z=24, R(F2)=0.0633) was solved from synchrotron powder diffraction data by applying a combination of direct methods, Patterson syntheses, and difference Fourier maps adding the unit cell information derived from electron diffraction and symmetry information obtained from 31P solid-state NMR spectroscopy. The structure of SrP2N4 was refined by the Rietveld method by utilizing both neutron and synchrotron X-ray powder diffraction data, and has been corroborated additionally by 31P solid-state NMR spectroscopy by employing through-bond connectivities and distance relations.     

Synthesis and Characterization of Polyether Adducts of Barium and Strontium Carboxylates and Their Use in the Formation of MTiO(3) Films

The synthesis, characterization, and reactivity of new polyether adducts of strontium and barium carboxylates of general composition M(O(2)CCF(3))(n)()(L) (M = Ba, L = 15-crown-5, (1); M = Ba (2), Sr (3), respectively, with L = tetraglyme are reported. The compounds were synthesized by reaction of BaCO(3) or MH(2) (M = Sr or Ba) with organic acids in the presence of the polyether ligands. These compounds have been characterized by IR and (13)C and (1)H NMR spectroscopies, elemental analyses, and thermogravimetric analysis. The species Ba(2)(O(2)CCF(3))(4)(15-crown-5)(2) (1) and [Ba(2)(O(2)CCF(3))(4)(tetraglyme)](infinity) (2), were also characterized by single-crystal X-ray diffraction. Ba(2)(O(2)CCF(3))(4)(15-crown-5)(2) (1) crystallizes in the orthorhombic space group Cccm with cell dimensions of a = 13.949(1) ?, b = 19.376(2) ?, c = 16.029(1) ?, and Z = 8. [Ba(2)(O(2)CCF(3))(4)(tetraglyme)](infinity) (2) crystallizes in the monoclinic space group C2/c with cell dimensions of a = 12.8673(12) ?, b = 16.6981(13) ?, c = 15.1191(12) ?, beta = 99.049(8) degrees, and Z = 4. Compounds 1-3 thermally decompose at high temperatures in the solid state to give MF(2). However, solutions of compounds 1-3 dissolved in ethanol with Ti(O-i-Pr)(4) give crystalline perovskite phase MTiO(3) films, or in the case of mixtures of 2 and 3, Ba(1)(-)(x)()Sr(x)()TiO(3) films below 600 degrees C when spin coated onto silicon substrates and thermally treated. The crystallinity, purity, and elemental composition of the films was determined by glancing angle X-ray diffraction and Auger electron spectroscopy.     

Structure and Vibrational Spectra of a New Acidic Diphosphate K2Cu(H2P2O7)2·2H2O

Abstract

Crystals of the acidic diphosphate K2Cu(H2P2O7)2 · 2 H2O, dipotassium copper bis(dihydrogendiphosphate) dihydrate, obtained via two different syntheses, revealed by means of single-crystal X-ray diffraction to be polymorph within triclinic Pī (a = 6.8560(4), b = 7.3140(3), c = 7.5570(4) Å; α = 81.028(4)°, β = 72.327(5)°, γ = 83.697(5)°, V = 355.86(3)Å3) and orthorhombic Pnma (a = 9.8990(6), b = 10.7810(7), c = 13.4010(7) Å, α = β = γ = 90°, V = 1430.17(15) Å3) space groups. Both phases were analyzed by FT-IR and micro-Raman vibrational spectroscopy and interpreted using factor group analysis. No coincidences of majority of the Raman and infrared spectral bands of K2Cu(H2P2O7)2 · 2 H2O confirmed the centrosymmetric structure of these two materials. The vibrational spectra point to a bent POP bridge angle.     

Structural and spectroscopic trends in actinyl iodates of uranium,neptunium, and plutonium

Two neptunyl(VI) iodates, NpO(2)(IO(3))(2)(H(2)O) (1) and NpO(2)(IO(3))(2).H(2)O (2), have been prepared from the aqueous reactions of Np(V) in HCl with KIO(4) or H(5)IO(6) at 180 degrees C and have been characterized by single crystal X-ray diffraction and Raman spectroscopy. Both compounds consist of two-dimensional arrangements of pentagonal bipyramidal [NpO(7)] polyhedra with axial neptunyl, NpO(2)(2+), dioxocations. In 1, the neptunium centers are bound in the equatorial plane by four bridging iodate anions and one terminal water molecule. The iodate anions link the [NpO(7)] units into corrugated sheets that interact with one another through intermolecular IO(3)(-)...IO(3)(-) interactions as also observed in UO(2)(IO(3))(2)(H(2)O). Compound 2 is isostructural with the recently reported PuO(2)(IO(3))(2).H(2)O, where oxygen atoms from bridging iodate anions occupy the five equatorial sites around the neptunyl moieties. The iodate anions occur as both mu(2)- and mu(3)-units and link the neptunyl polyhedra into sheets. Both types of iodate anions have their stereochemically active lone-pair of electrons aligned on one side of each layer creating a polar structure. Raman spectra of 1, UO(2)(IO(3))(2)(H(2)O), and PuO(2)(IO(3))(2).H(2)O show a sequential shift of the nu(1)(AnO(2)(2+)) stretch to lower wavenumber as the atomic number of the actinide is increased. Crystallographic data: 1, orthorhombic, space group Pcan, a = 7.684(2) A, b = 8.450(2) A, c = 12.493(3) A, Z = 4; 2, orthorhombic, space group Pna2(1), a = 7.314(1) A, b = 11.631(2) A, c = 9.449(2) A, Z = 4.     

Solvation structure of Li+ in concentrated LiPF6-propylene carbonate solutions

Time-of-flight neutron diffraction measurements were carried out for 6Li/7Li isotopically substituted 10 mol % LiPF6-propylene carbonate-d6 (PC-d6) solutions, in order to obtain structural information on the first solvation shell of Li+. Structural parameters concerning the nearest neighbor Li+...PC and Li+...PF6- interactions were determined through least-squares fitting analysis of the observed difference function, DeltaLi(Q). It has been revealed that the first solvation shell of Li+ consists in average of 4.5(1) PC molecules with an intermolecular Li+...O(PC) distance of 2.04(1) A. The angle Li+...O=C bond angle has been determined to be 138(2) degrees.     

Trifluoromethyl chlorosulfonate, CF3OSO2Cl: gas phase and crystal structure, conformation and vibrational analysis studied by experimental and theoretical methods

The geometric structure and conformational properties of trifluoromethyl chlorosulfonate (chlorosulfuric acid trifluoromethyl ester), CF(3)OSO(2)Cl, have been determined by X-ray crystallography, gas electron diffraction (GED), and vibrational spectroscopy (IR(gas), IR(matrix), and Raman(liquid)). These experimental investigations were supplemented by quantum chemical calculations (B3LYP with 6-311G* and 6-311+G(3df) basis sets). All experimental methods result in a single conformer with gauche orientation of the CF(3) group relative to the S[bond]Cl. The dihedral angle delta(COSCl) is determined to be 91.7(3) degrees in the crystal and 94(3) degrees in the gas phase. This dihedral angle corresponds to a near-eclipsed orientation of the O[bond]C relative to one of the S[double bond]O bonds (delta(CO[bond]SO) = -23.0(3) degrees and -21(3) degrees in the crystal and gas phase, respectively).     

Rich pseudopolymorphic behavior of the tetranuclear [Ni4(dpyatriz)2(NO3)8] complex

Reaction of nickel(II) nitrate with the dpyatriz ligand, namely 2,4,6-tris(bis(pyridin-2-yl)amino)-1,3,5-triazine, in acetonitrile produces a tetranuclear NiII coordination compound, [Ni4(dpyatriz)2(NO3)8(CH3CN)2(H2O)2].2CH3CN (1), the crystal structure of which has been determined by X-ray diffraction using a synchrotron source. 1 has been characterized by IR and UV-vis spectroscopy, elemental and thermogravimetric analyses, and magnetic susceptibility measurements. Its solid-state structure exhibits remarkable anion...pi interactions between coordinated nitrate ions and the triazine rings. In addition, a thorough X-ray powder diffraction study has revealed a number of pseudopolymorphic phases (2-5), resulting from various degrees of hydration/solvation of the [Ni4(dpyatriz)2] core. The interconversion scheme among the different phases has been determined using controlled heating, and the basic structural features of the different pseudopolymorphs have been assessed through ab initio powder diffraction methods.     

Cation-controlled assembly of Na+-linked lacunary alpha-Keggin tungstosilicates

Two novel salts of lacunary tungstosilicates with guanidinium and alkali metal cations, (CH6N3)7Na[SiW11O39].(CH3)2CO.8H2O (1) and (CH6N3)K6Na[SiW11O39].11.5H2O (2), have been synthesized and their crystal structures have been determined by synchrotron X-ray diffraction. In both crystals, the Na+ cations link the lacunary Keggin-type tungstosilicate anions into linear structures. The neighboring [SiW11O39]8- anions are related by two-fold screw and translational operations in compounds 1 and 2, respectively. Second harmonic generation was observed for compound 1.     

Thermal and Structural Behavior of Milk Fat

The thermal and structural properties of unstable varieties of triacylglycerols (TGs) crystallizing in milk fat globules of cream are examined in the range -8- +50 degrees C using a new instrument allowing simultaneously time-resolved synchrotron X-ray diffraction at both wide and small angles as a function of temperature (XRDT) and high sensitivity differential scanning calorimetry (DSC). Small angle X-ray diffraction shows that the unstable alpha form first formed by cream quenching to -8 degrees C corresponds in fact to two different lamellar phases corresponding to 2L (47 ?) and 3L (70.4 ?) arrangements of TGs. The bilayered structure is very unstable since it disappears during the course of a 20-min isothermal conditioning at -8 degrees C. On fast heating, the crystalline evolution of cream TGs demonstrates the monotropic character of their polymorphism. The structural and thermal behaviors of cream which are compared to that of its anhydrous milk fat isolated from the cream (C. Lopez et al., J. Dairy Sci., submitted) show that the crystallization occurring in emulsion droplets is similar to bulk. However, the comparison of XRD peak widths indicates that the TG crystallization is more disordered in emulsion. This disorder is attributed to the constraints due to the interface curvature in emulsion droplets. Copyright 2000 Academic Press.