Showing papers on "Molecular solid published in 1980"
TL;DR: In this article, the authors discuss single molecule properties and intermolecular interactions and discuss in detail the ortho-para properties, conversion and diffusion, followed by a description of the crystal structures and the orientational ordering phenomena.
Abstract: The molecular hydrogens (${\mathrm{H}}_{2}$, ${\mathrm{D}}_{2}$, HD, etc.) form the simplest of all molecular solids. The combination of the light mass, small moment of inertia, weak interactions, and the quasi-metastable ortho-para species result in a fascinating low-temperature behavior that can be understood to a large extent from considerations of first principles. After discussing single molecule properties and intermolecular interactions we discuss in detail the ortho-para properties, conversion and diffusion. This is followed by a description of the crystal structures and the orientational ordering phenomena. The thermodynamic properties are reviewed. The article is concluded with a discussion of the translational ground state of the solid and the effect of the large zero-point motion on the solid state properties. A large number of data are collected in tables and graphs to provide a reference source.
912 citations
TL;DR: In this article, a new type of density dependent spectroscopy is developed and applied to the study of acoustics phonons and excited state-phonon interactions in molecular crystals.
Abstract: A new type of density dependent spectroscopy is developed and applied to the study of acoustics phonons and excited state–phonon interactions in molecular crystals. It is shown that intermolecular separations in solids can be varied in a controlled manner along a selected crystalline direction and that the consequences of the molecular displacements can be observed optically in time‐resolved transient grating, absorption, and fluorescence experiments. The technique involves the generation of specific acoustic waves (phonon modes of definite wave vector) by transient grating optical excitation of the sample. The resulting time‐dependent density changes cause time‐varying spectral shifts, the magnitude of which are dependent on the detailed nature of the anisotropic intermolecular interactions in the crystal, e.g., anisotropic van der Waals interactions in molecular crystals can be directly investigated. First a formalism is presented which permits the determination of the nature of the phonons produced (lo...
134 citations
TL;DR: In this article, the authors investigated the glass transition phenomena occurring in stable crystalline phases of SnCl2 and found that these glassy crystals differ from those realized in undercooled metastable phases in that they never encounter the Kauzmann paradox and are considered to belong to a new category of aggregation of matter.
Abstract: It has previously been shown that the ordinary liquid–glass transition is just one example of a class of “glass transitions” due to loss of equilibrium which may occur widely in metastable phases of condensed matter. In the present paper, glass-transition phenomena occurring in stable crystalline phases of SnCl2.2H2O, H3BO3, H2O, pinacol hexahydrate, CO and TINO2 crystals are investigated. Deuteration effects on the kinetic properties of the freezing process are also reported. These glassy crystals differ from those realized in undercooled metastable phases in that they never encounter the Kauzmann paradox and are considered to belong to a new category of the state of aggregation of matter. Throughout the present studies, the usefulness of adiabatic calorimetry for the investigation of slow molecular motion in solids will be stressed, for which conventional spectroscopic techniques such as dielectric measurement are impractical because of the prolonged relaxation time.
102 citations
Book•
30 Jun 1980
TL;DR: In this article, an experimental study of Rotational and Vibrational Relaxation in liquid solids from the investigation of the IR and Raman vibrational profiles is presented.
Abstract: I Introduction.- Intermolecular Forces.- II Liquids.- Infrared and Raman Study of Vibrational Relaxation in Liquids.- Rotational Spectral Band Shapes in Dense Fluids.- Computer Calculation of Vibrational Band Profiles in Liquids.- Vibrational Relaxation of Hydrogen-bonded Species in Solution: Fine Structure of the ?s(XH) Band.- Experimental Study of Rotational and Vibrational Relaxation in Liquids from Investigation of the IR and Raman Vibrational Profiles.- Collision-Induced Vibrational Spectroscopy in Liquids.- Picosecond Vibrational Spectroscopy.- Vibrational Bandshapes in Viscous Liquids and Glasses.- The Study of Vibrational Relaxation by Ultrasonic and Light Scattering Techniques.- III Solids.- The Dynamics of Molecular Crystals: I. General Theory.- The Dynamics of Molecular Crystals: II. Intermolecular Potentials.- The Dynamics of Molecular Crystals: III. Infrared and Raman Intensity of Lattice Bands.- The Dynamics of Molecular Crystals: IV. Hamiltonian Perturbation Treatment.- Large Amplitude Motions in Molecular Crystals.- Raman and Infrared Lineshapes of Internal Modes in ODIC Phases.- Vibrational Band Shapes of Amorphous Solids.- Order-Disorder Phase Transitions in Solids.- The Effect of Multiphonon Processes on Vibrational Band Shapes in Molecular Solids.- Neutron Spectroscopy Studies on Rotational States in Molecular Solids.- Rotation-translation Coupling in Collective Modes of Molecular Solids and Liquids.- Participants.- Author Index.- Substance Index.
100 citations
TL;DR: In this paper, a cylindrical NMR sample spinner employing gas bearings is described and its application to high-resolution deuterium NMR in solids by magic angle spinning is demonstrated.
33 citations
TL;DR: In this paper, the structures of van der Waals molecules are viewed using simple molecular orbital ideas, and the observed geometry is the one where the molecular orbital based repulsion of closed shells of electrons is minimized, i.e., the angular geometry is determined by covalent rather than van derWaals forces.
Abstract: The structures of van der Waals molecules are viewed using simple molecular orbital ideas. In most cases studied the observed geometry is the one where the molecular orbital based repulsion of closed shells of electrons is minimized, i.e., the angular geometry is determined by covalent rather than van der Waals forces. In some, but not all, cases there is an attractive contribution to the energy arising via HOMO–LUMO interaction between orbitals located on the inert gas atom and the molecule to which it is coordinated as suggested by Klemperer. The following systems were studied: ArX2 (X2=Cl2, N2, O2, HCl, ClF), (X2)2, (X2=Cl2, N2, O2, CO2), and ArBF3.
14 citations
TL;DR: In this paper, the simultaneous propagation of lattice phonons and photons in molecular crystals is discussed and an equation of propagation of the modes involving molecular displacements and an electric field is derived based on the concept of dynamic multipoles and taking into account retardation effects.
Abstract: The simultaneous propagation of lattice phonons and photons in molecular crystals is discussed The equation of propagation of the modes involving molecular displacements and an electric field is derived based on the concept of dynamic multipoles and taking into account retardation effects The equation is analyzed mainly in a long wave limit in order to study the optical properties of lattice phonons The elastic and piezoelectric constants are then obtained in terms of molecular parameters of the model Finally, as an example, the polariton spectrum of crystalline HCN is analyzed
9 citations
TL;DR: In this article, a novel observation of magnetic superexchange interactions in disordered molecular solid is reported, where coordinated electrical conductivity and electron spin resonance measurements are made on controlled, variable concentrations of the molecule trip-p -tolylamine and its paramagnetic radical cation, molecularly dispersed in a polymer matrix.
8 citations
TL;DR: In this paper, the manybody contributions to the OK binding energy of solid Argon were discussed in terms of Aziz-Chen 13 potential, and the many-body contributions were analyzed using Aziz−Chen−13 potential.
Abstract: The many‐body contributions to the OK binding energy of solid Argon are discussed in terms of Aziz‐Chen 13 potential.(AIP)
4 citations
TL;DR: In this paper, the structure of the transmission coefficient for 0-15 eV monoenergetic electrons passing through thin film (approximately 150 AA) molecular solids is interpreted to arise from the formation of electron-exciton complexes.
Abstract: Structure in the transmission coefficient for 0-15 eV monoenergetic electrons passing through thin film ( approximately 150 AA) molecular solids is interpreted to arise from the formation of electron-exciton complexes. The existence of such coupled states is also shown to be consistent with delayed fluorescence and photocurrent experiments in molecular solids. New transmission spectra are reported in 1,3,5,7-cyclo-octatetraene.
TL;DR: In this article, the transmission coefficient for monoenergetic electrons passing through thin films (∼100 A) of molecular solids is measured as a function of electron energy in the range 0.04 eV FWHM.
Abstract: The transmission coefficient for monoenergetic electrons (0.04 eV FWHM) passing through thin films (∼100 A) of molecular solids is measured as a function of electron energy in the range 0–15 eV. The visibility of sharp maxima in the transmission spectra is enhanced by measuring the negative value of the second energy derivative of the transmitted current with respect to electron energy. In benzene, fluorobenzene, pyridine, benzaldehyde, furan, cyclohexene and 1,3‐ and 1,4‐cyclohexadiene, the spectra exhibit from six to eight maxima, whereas in pyrrole and thiophene four structures are resolved. With the exception of the first two features in fluorobenzene and the first feature for the other solids investigated, all other maxima correlate within at least ±0.5 eV with the gas‐phase electronic transitions. This correlation is achieved by increasing the energy scale of the transmission spectra relative to the gas‐phase electronic energy levels. These findings corroborate previous experiments on solid organic films by Hamill and co‐workers who attributed peaks in the first energy derivative of the transmitted current to energy‐loss events. It is shown that the transmission features can arise either from an increase in the overall transmission coefficient due to the production of inelastically scattered electrons or from the formation of an electron–exciton complex through the temporary capture of an injected excess electron by field of a Frenkel exciton. The first low‐energy feature in each spectrum may possibly arise from an enhancement of vibrational excitation related to the energy dependence of the structure factor.
01 Jan 1980
TL;DR: In this article, the preparation and structural chemistry of a very restricted class of solid transition metal compounds is described, consisting of only mixed valence solids containing finite linear arrays of nonbridged transition metal ions.
Abstract: This article describes the preparation and structural chemistry of a very restricted class of solid transition metal compounds. Onlymixed valence solids containinginfinite linear arrays of nonbridged transition metal ions will be discussed. The paper is limited to these materials, because high and anisotropic conductivities in linear molecular solids can only be expected fromdirectly interacting systems (1d metals).
01 Jan 1980
TL;DR: In this paper, the collective modes, particularly the shear modes, can be strongly influenced by molecular reorientation, and the coupling of shear waves to reorientational motion in a molecular dynamics (MD) computer simulation study of liquid H2O is considered.
Abstract: This article is concerned with rotation-translation coupling in molecular solids and liquids. We first review some of the computer simulation work carried out on solid and liquid N2 using atom-atom potentials (1–4). We show that the collective modes, particularly the shear modes, can be strongly influenced by molecular reorientation. Next we recall briefly some experimental data on depolarized light scattering from supercooled fluids which show evidence of transverse hydrodynamic modes (5,6). The coupling of shear waves to reorientational motion in a molecular dynamics (MD) computer simulation study of liquid H2O is then considered (7). Finally, by analogy with the dynamics of a two-component ionic fluid (8) a method is suggested for studying the coupling of shear waves to molecular reorientation in a more systematic fashion.
01 Jan 1980
TL;DR: In this paper, a brief review is given on recent far infrared spectroscopic works under pressure, and some technological problems are discussed, particularly the need for a window material combining high pressure resistance and good optical transmission.
Abstract: A brief review is given on recent far infrared spectroscopic works under pressure. Some technological problems are discussed, particularly the need for a window material combining high pressure resistance and good optical transmission. Collision induced absorption spectra as well as typical pressure effects on phase transitions and phonon spectra in molecular solids are presented.
01 Jan 1980
TL;DR: In this article, the electron concept is generalised by delocalisation of the excitation over the whole system, which is polarised by the radiation field, with formation of polariton states.
Abstract: We give below a formal, through elementary account of the principal phenomena observed recently in aromatic, molecular, ordered systems, where the electron concept is generalised by delocalisation of the excitation over the whole system, which is polarised by the radiation field, with formation of. polariton states prospects for new calculations are suggested.
01 Jan 1980
TL;DR: In this paper, a brief introduction to the information which neutron spectroscopy can provide on condensed particle systems and, secondly, some examples of information obtained by neutron Spectroscopy: a) on single particle rotational motions in molecular solids, b) on collective motions in disordered orientational coordinates.
Abstract: This lecture presents first a brief introduction to the information which neutron spectroscopy can provide on condensed particle systems and, secondly, some examples of information obtained by neutron spectroscopy: a) on single particle rotational motions in molecular solids, b) on collective motions in disordered orientational coordinates. By collective motions we mean motions with phase relations in the displacements of neighbouring particles; such phase relations usually are expected for ordered systems only. By single particle motions we mean motions without such phase relations.
01 Jan 1980