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The amplification of microscopic molecular motions so as to produce a controlled macroscopic body effect is the main challenge in the development of molecular mechanical devices. That amplification requires the coherent and ordered movement of each molecule of a whole macroscopic set, such as that taking place in a single-crystal-to-single-crystal transition. Actually, single-crystal-to-single-crystal transitions in molecular crystals can produce a variety of mechanical effects potentially useful in the development of smart materials. A challenging issue in these dynamic crystals, propedeutic to many possible applications in devices, is the gaining of a strict control over the mechanical effects associated with the transition. Here we report an example in which the control of the mechanical effects was successfully obtained. The compound studied undergoes a reversible single-crystal-to-single-crystal transition at 71 °C, from a planar stacked to a herringbone type packing. To this transition, a reversible macroscopic self-reshaping of the crystal is associated. Depending on the morphology, the crystal specimen undergoes a reversible longitudinal expansion of about 20% or a reversible transverse expansion of 20%, the other two dimensions of the crystal specimen being substantially unchanged. The amount of the macroscopic reshaping effect (20%) fully matches the relative variation of the sole unit cell parameter that changes during the transition (from 8.139 to 9.666 Å) in a sort of scale-invariant process. This represents striking evidence of controlled translation of sub-nanometer molecular motions up to the macroscopic scale of body motion.

Here we report the solid-state experimental and computational analysis of naphtho[2,3-c][1,2,5]thiadiazole (1) and naphtho[2,3- c][1,2,5]selenadiazole (2) showing that the three different crystal phases of polymorphic 1 and the sole crystal phase of nonpolymorphic 2 are characterized by predominance of some intermolecular motifs over the others. In particular, the intermolecular interactions present in the compounds, π···π, C−H···π, C−H···N, S···N, and Se···N, are hierarchically ranked, in such a way that in 1 polymorphism is observed, with the three different phases showing different combinations of the intermolecular interactions, while in 2 only the packing that maximizes the strongest intermolecular interaction by far, i.e., chalcogen bond, is observed. Moreover we also show that different packings produce different responses in the solid-state topochemical reactivity of the crystalline compounds, spanning from nonreactive packings to packings producing butterfly dimers. In order to rationalize the different responses, the relevance of the transverse parallel shift of molecules is suggested, as an important factor, in addition to the known Schmidt’s rules for solid-state topochemical reactions.

The sole crystal structure generally observed for a chemical compound (actual crystal structure) corresponds to only one of the many minima present in the crystal energy landscape of that compound. A challenging problem of crystallography is to explain why the many other possible crystal structures (in terms of energy and density) present in the landscape (virtual structures) are not observed as polymorphs. In the present paper, with specific reference to semicarbazides of substituted benzoic acids, the concept of actual and virtual structures is extended and it is proven that optimization of a molecule in a different crystal packing of another molecule (interchangeability of molecules and packings) can lead to low minima of the lattice energy and to a high lattice density also in the case of molecules significantly different in shape (para/meta substituted compounds). This suggests that a crystal structure can be viewed as a sort of elastic system that can be deformed to fit molecules of different electronic character and shape. Surprisingly, in many cases, this deformation is accomplished at low cost of energy and density. Our results also suggest that the small number of polymorphs cannot be explained only by inspection of the crystal energy landscape, which would otherwise suggest many, but also, and perhaps mostly, by the analysis of the initial steps of crystal formation even before nucleation, when many different molecular clusters corresponding to different packings are in competition with each other.

Imines obtained by condensation of 4-hydroxybenzohydrazide with aliphatic ketones are a rare example of a class of compounds showing a remarkable tendency to crystallize in acentric polar space groups (Pna21 or Cc). In fact, all of the (seven) compounds studied up to now show at least one polar polymorph. In some cases, polymorphism was detected, and a nonpolar centrosymmetric phase was also identified (P21/c or P21/n space group). With the aim to disclose the conditions that can favor the formation of acentric structures in molecular crystals, we report, in this paper, a theoretical analysis (ab initio density functional theory with periodic boundary) of the lattice energy and density of all the packing modes observed in the whole set of imines. The computational analysis has been performed by optimizing each compound in its own experimental packings (actual crystal structures) and also in the packings of the other compounds of the class (virtual structures). The experimental crystallographic data and the theoretical analysis suggest that two conformers, basically differing for the orientation of the phenolic H atom in the plane of the phenyl ring, compete, in solution, for the formation of polar or centrosymmetric packings. The transitions between polar and centrosymmetric polymorphs are of diffusive type, and single crystals are not preserved, while the transitions between different polar polymorphs can be of single-crystal-to-single-crystal type.

Reaction of N-rich conjugated bis(3,4-diamino-1,2,4-triazole)s with dilute hydrochloric acid affords bis(3,4-diamino-1,2,4-triazol-2-ium)chlorides. These compounds form layered structures in which planar layers of molecules are parallelly stacked. The π-stacking distance of the layers is relatively short, as compared with all-carbon-containing aromatic compounds, ranging between 3.00 and 3.22 Å at 173 K, and several contacts shorter than the sum of van der Waals radii are observed in the crystal structures. The features of the crystal structures are discussed in terms of the high nitrogen content of the compounds and of the H-bonding patterns. Periodic ab initio theoretical calculations of the crystal structures have allowed decomposing the lattice energy into various contributions in order to put up the relevance of van der Waals interactions for the π-stacking. In particular, it is found that van der Waals interactions account for about 10% of the total lattice energy and about 50% of the stacking energy (interlayer energy).

Maximum Probability Domain (MPD) analysis has been recently applied to pure covalent and ionic crystals. The present study is devoted to a first MPD analysis of semi ionic crystals, Silicon Oxide, Aluminum Oxide and Titanium Oxide. These crystals are involved in important catalytic and photo-catalytic processes occurring on their surfaces. For this reason the study has been performed on bulk crystal and on surface slab models. Also surface neutral oxygen vacancy, the F-0 surface defect, has been considered. The Electron Localization Function (ELF) analysis has also been performed, due to its holistic approach to electronic structures. (C) 2015 Published by Elsevier BM.

The present study discusses the main features of the two programs CRYSTAL and EMBED developed for the ab initio study of the electronic properties of perfect periodic structures and of crystals with local defects, respectively. After a brief historical introduction, the structure of CRYSTAL is outlined and some specific aspects are discussed in detail: the use of local basis functions, the way of dealing with the Coulomb and the exchange series, the exploitation of point symmetry, the possibility to adopt either the Hartree–Fock approach or one among a variety of Kohn–Sham Hamiltonians. The present capabilities of the program are illustrated by a survey of selected applications from existing literature. Information is provided concerning work in progress aimed at removing some of the limitations of the code and improving its performance. The characteristics of EMBED are analyzed with emphasis given to the critical aspects of the method: limits of validity of the fundamental approximation on which the embedding technique relies, problems of convergence of the self-consistent procedure; and the delicate issue of the estimate of the defect formation energy. Again, a critical survey of applications clarifies the capabilities of the code. The envisaged improvements to be introduced in a forthcoming release of EMBED are presented. The present and prospective role of the two programs in the field of computational studies of condensed matter problems is outlined. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 77: 1032–1048, 2000

The capabilities of the CRYSTAL14 program are presented, and the improvements made with respect to the previous CRYSTAL09 version discussed. CRYSTAL14 is an ab initio code that uses a Gaussian-type basis set: both pseudopotential and all-electron strategies are permitted; the latter is not much more expensive than the former up to the first-second transition metal rows of the periodic table. A variety of density functionals is available, including as an extreme case Hartree-Fock; hybrids of various nature (global, range-separated, double) can be used. In particular, a very efficient implementation of global hybrids, such as popular B3LYP and PBE0 prescriptions, allows for such calculations to be performed at relatively low computational cost. The program can treat on the same grounds zero-dimensional (molecules), one-dimensional (polymers), two-dimensional (slabs), as well as three-dimensional (3D; crystals) systems. No spurious 3D periodicity is required for low-dimensional systems as happens when plane-waves are used as a basis set. Symmetry is fully exploited at all steps of the calculation; this permits, for example, to investigate nanotubes of increasing radius at a nearly constant cost (better than linear scaling!) or to perform self-consistent-field (SCF) calculations on fullerenes as large as (10,10), with 6000 atoms, 84,000 atomic orbitals, and 20 SCF cycles, on a single core in one day. Three versions of the code exist, serial, parallel, and massive-parallel. In the second one, the most relevant matrices are duplicated, whereas in the third one the matrices in reciprocal space are distributed for diagonalization. All the relevant vectors are now dynamically allocated and deallocated after use, making CRYSTAL14 much more agile than the previous version, in which they were statically allocated. The program now fits more easily in low-memory machines (as many supercomputers nowadays are). CRYSTAL14 can be used on parallel machines up to a high number of cores (benchmarks up to 10,240 cores are documented) with good scalability, the main limitation remaining the diagonalization step. Many tensorial properties can be evaluated in a fully automated way by using a single input keyword: elastic, piezoelectric, photoelastic, dielectric, as well as first and second hyperpolarizabilies, electric field gradients, Born tensors and so forth. Many tools permit a complete analysis of the vibrational properties of crystalline compounds. The infrared and Raman intensities are now computed analytically and related spectra can be generated. Isotopic shifts are easily evaluated, frequencies of only a fragment of a large system computed and nuclear contribution to the dielectric tensor determined. New algorithms have been devised for the investigation of solid solutions and disordered systems. The topological analysis of the electron charge density, according to the Quantum Theory of Atoms in Molecules, is now incorporated in the code via the integrated merge of the TOPOND package. Electron correlation can be evaluated at the Moller-Plesset second-order level (namely MP2) and a set of double-hybrids are presently available via the integrated merge with the CRYSCOR program. (C) 2014 Wiley Periodicals, Inc.

Semicarbazides of p-substituted benzoic acids are a class of simple molecules endowed with H-bonding donor and acceptor groups capable of forming H-bonded rows along three linearly independent directions (orthogonal H-bonding synthons). When the acceptor group at the para position is strong (–NO2, –CN, –N=) the same crystal packing is observed, in which three linearly independent chains are formed, and the lattice parameters are easily predictable. In the case of halogen atoms at the para position (–F, –Cl) two different packings are observed in which only one or two H-bonded chains are present. Through ab initio periodic DFT-LCAO computations, we have calculated the lattice energy and density of each semicarbazide in each of the three packings, constructing the matrices Uij and ρij of the lattice energy and density. It is found that all of the different modes of packing observed experimentally for single members of the class correspond to minima of the lattice energy and to acceptable lattice densities for every member of the class.

The wave functions of boron, aluminium and gallium phosphides have been calculated at both the Hartree - Fock and local density approximation levels using the ab initio linear combination of atomic orbitals method implemented in the program CRYSTAL. The Mulliken populations, bandstructure, electron charge densities, and structure factors are evaluated and compared. The chemical bonds are mainly covalent, as revealed by the difference electron charge-density maps obtained by subtracting from the total densities the superposition of the spherical atomic densities. A charge-density accumulation between the nearest neighbours slightly shifted towards the phosphorus appears in the AlP and GaP compounds, whereas an opposite charge transfer from phosphorus to boron is observed in boron phosphide from the Mulliken population analysis.

Two new perylene diimide derivatives N,N′-bis(5-tridecyl-1,3,4- thiadiazol-2-yl)perylene-3,4,9,10-tetracarboxylic 3,4:9,10-diimide (PDI-T1) and N,N′-bis[5-(1-hexyl)nonyl-1,3,4-thiadiazol-2-yl]perylene-3,4,9, 10-tetracarboxylic 3,4:9,10-diimide (PDI-T2), achieved by functionalizing the basic perylene molecular core at imide nitrogen with 1,3,4-thiadiazole rings, have been synthesized. Both these compounds make possible the fabrication of n-type organic thin-film transistors able to work in air, even when bare SiO2 surfaces are utilized as gate dielectric. As active channels of transistors in the bottom-contact bottom-gate configuration, PDI-T1 evaporated films exhibited a maximum mobility of 0.016 cm2/V s in vacuum. For evaporated PDI-T2 films, instead, mobility values were found to be more than one order of magnitude lower, because of their reduced degree of crystalline order. However, PDI-T2 films can be also deposited by solution techniques and field-effect transistors were fabricated by spin-coating, displaying mobility values ranging between 10-6 and 10-5 cm2/V s. Similar to what previously found for other perylene diimide derivatives, our experimental work also demonstrates that the electrical response of both PDI-T1 and PDI-T2 transistors under ambient conditions can be improved by increasing the level of hydrophobicity of the dielectric surface. © 2012 Elsevier B.V. All rights reserved.

The effect of the Madelung field corresponding to formal point charges ± e arranged according to the fcc lattice of LiF upon CO, N2 and NO molecules is studied in order to isolate the purely electrostatic interaction from the other forces acting in the related physisorption processes. The polarization which is produced in those molecules by the Madelung field is analyzed in terms of dipole and quadrupole moments, as well as in terms of electron charge distributions. The influence of the electron correlation is taken into account by using the QCISD technique, which requires the semi-infinite lattice being simulated with a suitable cluster of point charges.

The static structural properties and B1-B2 phase transition of SrO were calculated at an ab initio level within the Hartree-Fock (HF) approximation using the effective core potential. The HF data were corrected a posteriori by integrating the HF charge density according to the correlation---only gradient-density-functional formulas proposed by Colle and Salvetti [Theor. Chim. Acta 37, 329 (1975)] and by Perdew [J. P. Perdew, Electronic Structure of Solids, edited by P. Ziesche and H. Eschring (Akademie Verlag, Berlin, in press)]. The HF binding energy, structural parameters, lattice parameter, bulk modulus, and elastic constants are in reasonable agreement with experiment. The correlation correction brings the binding energy into better agreement with the experiment. The transition pressure between B1 and B2 phases is in good agreement with the experimental value at the HF level, whereas it is corrected poorly by the addition of an a posteriori correlation correction.

The electronic structure of different magnetic states of alpha, beta and gamma modifications of TiCl(3) has been computed employing the density functional theory with periodic boundary conditions and localized Gaussian basis sets. The analysis of the density of the electronic states (DOS) and of the spin density makes it possible to classify these halides as Mott-Hubbard insulators, where the band gap appears a result of large on-site Coulomb interaction. For each crystalline phase, the relative stability of different magnetic states has been analyzed in terms of exchange mechanisms. The electronic population data along with the spin density maps support the assumption of a d(1) Titanium ion in a distorted octahedral crystal field, notwithstanding the not fully ionic character of TiCl(3) modifications. Dispersion forces are particularly important for this material: a classical correction (of the type f(R)/R(6)) has been added to the DFT energies and gradients, providing a good agreement with structural data.

In order to give a deeper insight into the cracking of the Verneuil corundum boules, several samples of different colors and from different industrial sources have been analyzed by means of white beam synchrotron radiation X-ray diffraction topography (WB-SR-XRDT) and PBC analysis (Hartman and Perdock theory). The cracking occurs along an irregular surface containing the elongation axis of boules, and the WB-SR-XRDT analysis shows that this surface is nearly parallel to the { 1 2 0 } crystallographic planes. Following Hartman and Perdock theory, these planes form F-planes with a high density of PBC directions: 3 PBC directions—[2 1 1], [2 1 0] and [ 4 2 1 ]—have been recognized as parallel to the 1 2 0 plane. The 1 02 planes that are normal to the cracking surface of boules are F-planes too, but they show a lower bond density per unit area with respect to the 1 2 0 planes. Ab initio calculations show that these planes have lower surface energies with respect to other hk 0 planes, such as {1 0 0} and {0 1 0}.

cited By 48; International audience; We present the results of a first principles study on the ordered Ge 0. 50C 0.50 and Sn 0.50C 0.50 cubic alloys. A linear combination of atomic orbitals approach in the framework of density functional theory is employed for total energy calculations in the zincblende phase. A fitting of the energy surface to the equation of state yields the lattice constant of 4.61 and 5.17 Å and the bulk modulus of 181 and 119 GPa for GeC and SnC, respectively. Analysis of band structure suggests a crossover of the nature of the band gap from indirect to direct in going from SiC to GeC to SnC. Although both alloys predicted to be unstable with respect to their elemental components at zero pressure and temperature, GeC appears to become stable at higher pressure. It appears that both the lattice constant and bulk modulus of the ordered alloys do not follow Végard's linear rule, though the calculated dielectric constant of the cubic alloys is approximately the average of the dielectric constant of their elemental components.

Bulk platinum and platinum slabs one to four (111) layers thick have been studied using the HF and DFT CO-LCAO (Hartree-Fock and density functional theory crystalline-orbital and linear-combination-of-atomic-orbitals) CRYSTAL program. The objective of this paper is to test the suitability of slabs of different thicknesses for modelling the (111) surface of platinum. The cohesive properties of the bulk (lattice constant, bulk modulus, cohesive energy) are reported and the electronic structure of the platinum bulk is discussed. The surface and relaxation energies as well as the relaxation distances of the slabs were evaluated. The electronic structure of the slabs is discussed in terms of Mulliken population analysis, the density of states, the band structure and electron-density difference maps. `Initial-state' surface-atom core-level shifts are reported, as well as atomic dipole and quadrupole moments perpendicular to the surface.

cited By 38; International audience; All electron density functional theory calculations were performed on the ordered Ge0.50Sn0.50 alloy in the zinc-blende phase to study its structural, electronic, and optical properties along with its stability with respect to the elemental components. We employed a linear combination of atomic orbitals approach for calculations in which the Bloch functions were constructed as linear combinations of atom-centered Gaussian orbitals. The calculated results show a relative stability of the GeSn alloy in the zinc-blende phase for which the lattice constant and bulk modulus are predicted to be 6.20 Å and 53 GPa, respectively. Analysis of band structure and density of states shows the cubic-ordered alloy to be a direct-gap semiconductor with a small band gap. The optical properties, such as dielectric constant and plasmon energy of the cubic alloy, appear to be about the average of the respective values in its elemental components. © 1999 American Institute of Physics.

International audience; The properties of hcp magnesium are investigated using the density functional method with the linear combination of atomic Orbitals as implemented in the CRYSTAL95 code. The lattice equilibrium parameters and the binding energy have been calculated at the Hartree-Fock level, at the hybrid Hartree-Fock density functional level, and at the Kohn-Sham density functional level using local and non-local exchange and correlation potentials. The electronic properties (band structures, topologies of the Fermi surface, and densities of states) and the elastic constants are computed for each type of functional, and compared to experimental data.

We present an analysis of local or semilocal density functionals for the exchange)correlation energy by decomposing them into their gradients r local Seitz s . . . radius , z relative spin polarization , and s reduced density gradient . We explain the numerical method pertaining to this kind of analysis and present results for a few atoms and ions. The atomic shell structure is prominent, and only the ranges 0 - r - 10 and s 0 - s - 3 are important. The low-density and large-gradient domains, where the approximations for the exchange)correlation energy are least trustworthy, have very little weight. Q 1997 John Wiley & Sons, Inc.

We present electronic and structural parameters for bulk rutile (TiO2) determined by means of different theoretical methods, namely, the periodic Hartree-Fock approach, subsequent post-Hartree-Fock density functional correlation correction, and a linear-combination-of-atomic-orbitals approach based entirely on density functionals. Differences between the use of effective core potentials, a frozen-core treatment, and all-electron calculations are investigated. (C) 1996 John Wiley & Sons, Inc.

All-electron Hartree - Fock and density functional calculations are performed to study the high-pressure phase transitions in gallium nitride and silicon within the framework of the linear combination of atomic orbitals using the Gaussian basis sets. Under high pressure, GaN makes a transition from the wurtzite (semiconducting) to the rock-salt (semiconducting) phase, whereas Si makes a transition from the cubic (semiconducting) to the -tin (metallic) phase. The calculated results suggest that the lattice constants and the bulk moduli can be accurately described by both the methodologies for GaN and Si. Furthermore, both the calculations yield a phase transition pressure for GaN which is in reasonable agreement with the experimental data. However, the transition pressure for Si calculated in the closed-shell (restricted) Hartree - Fock approximation differs significantly from the one calculated using the density functional theory and the experimental data. This is primarily due to the fact that the energy difference between a semiconducting and a metallic state of Si is not well produced in the closed-shell Hartree - Fock approximation.

The structural properties and the phase transition between the B1 (rock salt) and B2 (CsCl) phases of NaCl have been investigated at an ab initio level. Total energy curves, obtained with periodic Hartree-Fock (HF) calculations, have been corrected a posteriori by integrating the HF charge density according to the correlation-only density-functional-like formulae proposed by Colle and Salvetti (CS75) in 1975 and by Perdew in 1986 (P86) and 1991 (P91). The three functionals are 'non-local', containing terms that depend on the gradient of the electronic density. The correlation correction brings the HF data for the lattice energy (LE), lattice parameter (a(o)) and bulk modulus (B) into good agreement with experiment, the best performance being obtained with the most recent functional, P91 (the percentage error is +0.3%, -0.5% and +5.6% respectively for LE, a(o) and B). The HF transition pressure (39.2GPa) is slightly modified by the CS75 correction (37.2); P86 and P91 functionals reduce the computed value to 30.1 GPa and 28.9 GPa respectively, in better agreement with experiment (30 GPa).

Corundum, or alpha-Al2O3, is investigated at the ab initio periodic Hartree-Fock LCAO level using the program CRYSTAL. A split valence 6-21G basis set is adopted, and the influence of d polarization functions is explored. The four geometrical parameters of the unit cell are optimized, the difference with respect to the experimental data always being less than 1%. The electric field gradient tensor at both nuclei (Al and O) is calculated; agreement with the experimental data is quite satisfactory. Band structure, density of stages and charge density maps are also given. The resulting electronic structure is highly ionic.

Periodic pseudopotential Hartree–Fock calculations have been performed on the quartz structure of silica and germanium dioxide. It is shown that the tilt angle is the most important structural parameter. This parameter emphasizes the role of the oxygen polarization function which appear to be necessary to recover the correct geometry of low quartz. The structure of β‐quartz is rationalized on the basis of the energy dependence upon the tilt angle and the absence of β‐structure in GeO2 is explained. Finally the behavior of both oxides under pressure is discussed.

The regular adsorption of CO at various concentrations on an infinite three-layer slab of LiF has been studied by using the CRYSTAL ab initio program. The CO molecules are adsorbed vertically above the surface cations by purely electrostatic attraction counterbalanced by the Pauli repulsion. The induced polarization has been analysed through the changes occurring in the molecular orbitals of the adsorbed species. The adsorption via the oxygen atom appears to be preferred, which contradicts IR experimental data. Such contradiction arises from the correlation error in the Hartree-Fock SCF method which is applied in the CRYSTAL program. Consideration of simple correlated clusters enables a semi-quantitative evaluation which additively corrects the above contradictory results.

The electronic structure of corundum (α-Al 2 O 3 ) is calculated at the ab initio Hartree-Fock level. Cohesive energy, total and projected densities of states, atomic multipoles, bond populations and electron charge density distribution maps are given. The oxygen-aluminium bond is found to be partially covalent in nature; the atomic charges are −0.73 e and +1.09 e for O and Al respectively.

The MgO(001) surface has been studied with an ab initio Hartree-Fock crystalline orbital LCAO program. An optimized basis set containing nine atomic orbitals (three s and six p) per atom has been used. The semi-infinite crystal has been simulated by a slab containing three planes (six atoms per cell). In agreement with the most recent LEED experiments, no relaxation is found and the “rumpling” is very small (1% of the nearest neighbour separation in the bulk). The analysis of the electron charge distribution and of the ion multipoles shows that the fully ionic character found for the bulk is maintained at the surface, and that the anion deformation is very small. A surface energy of 1.43 J/m 2 was obtained.

The core pseudopotentials of Durand and Barthelat have been introduced in the periodic Hartree-Fock program CRYSTAL. This new option allows the treatment of crystals involving heavy atoms and therefore extends the applicability of the method. A comparison between all-electron and pseudopotential results is presented. Binding energies, optimized cell parameters, bulk moduli, band structures and electron density curves calculated with the two methods are presented for covalent (diamond and silicon), metallic (lithium) and ionic (MgO) systems. As expected the pseudopotential results for covalent compounds are in good agreement with those obtained from all-electron calculations; for MgO larger discrepancies are observed, possibly due to core polarization effects.

The expressions for the corrections to the frequency of the3P2−3P1 and3P1−3P0 π-transitions of Mg and Ca are derived, taking into account the anomalous magnetic moment of the electron as well as the diamagnetic term of the Hamiltonian. Numerical results for24Mg are given.

Ab initio Hartree-Fock calculations of the (0001) and (1010) crystal faces of α-alumina have been performed using a slab model and taking full account of two-dimensional periodicity. Surface relaxation, surface formation energy, Mulliken populations, charge density maps, and densities of states are obtained and discussed. The validity of the slab model is discussed by analyzing the dependence of results on slab thickness.

IR and Raman spectra of morpholine, a structure-directing agent, entrapped within the chabasite-related structures of both ALPO-34 and SAPO-34, are discussed. It is revealed that some vibrational features of the morpholine, which is present in the protonic form, are very sensitive to both host–guest (framework–morpholine) and guest–guest (morpholine–morpholine and morpholine–water) interactions occurring within the zeolites. FTIR spectroscopy shows that: (a) the NH 2 group of the protonated morpholine is H-bonded to the zeolitic frameworks (more strongly in SAPO-34); (b) the CH 2 vibrations in the 1500–1300 cm −1 region are sensitive to the surrounding being different for the ALPO-34 compared with the SAPO-34. Raman spectroscopy reveals that the ring-breathing mode of the morpholine has a small red-shift (from 822 cm −1 for the protonated molecule in solution, to 815 cm −1 in SAPO-34), and is deeply decreased in intensity when the molecule is in the constrained space of the zeolitic cages. In this case, two new modes at 472 and 245 cm −1 , tentatively assigned to morpholine–framework motions, are also present. IR and Raman bands are better resolved in the case of morpholine in ALPO-34 where the template–framework interactions are weaker.