Showing papers on "Molecular solid published in 1972"
TL;DR: The behavior of the Ps atom in molecular substances, particularly liquids, is investigated in this article, where the pickoff rates of oPs in various liquid compounds are found to have a simple empirical relationship to the values of the surface tension of the liquids.
Abstract: The behavior of the Ps atom in molecular substances, particularly liquids, is investigated. The pickoff rates of o‐Ps in various liquid compounds are found to have a simple empirical relationship to the values of the surface tension of the liquids. The relationship is found to have a theoretical foundation. The Ps atom is highly localized in a cavity created by the balance of various molecular forces inside the liquid. From the above relationship, other simple relationships between the pickoff rates of o‐Ps and the various properties of the medium, e.g., polarizability, cohesive energy density, etc., and the temperature or pressure changes can be derived and explained. The diffusion of o‐Ps is discussed. A similar approach can also be used for molecular solids.
1,731 citations
TL;DR: In this paper, the equation of state of hydrogen was calculated for specific volumes ranging from 0.01 to 0.0001 cm3/mole and for temperatures ranging from 200 to 1 million K.
53 citations
TL;DR: In this paper, the quantum mechanical lattice dynamics formalism developed in the preceding paper for molecular solids is applied to the librational modes at k=0 in solid α•N2, CO2, and o•H2, interacting through a quadrupole−quadrupole potential.
Abstract: The quantum mechanical lattice dynamics formalism developed in the preceding paper for molecular solids is applied to the librational modes at k=0 in solid α‐N2, CO2, and o‐H2, interacting through a quadrupole‐quadrupole potential. Librational wavefunctions are constructed for α‐N2 and CO2, and free rotor wavefunctions were used for librons in solid o‐H2. It is found that the quantum‐mechanical lattice frequencies provide nonnegligible, though not dramatic, corrections to the frequencies calculated in the classical harmonic approximation. For α‐N2 the quadrupole potential provides a satisfactory description of the anisotropic potential, with the quantum‐mechanical frequencies significantly closer to experiment than the classical ones. For CO2 the quadrupole potential provides only part of the anisotropic potential.
25 citations
TL;DR: In this article, the authors used thermally assisted hopping (tunneling) between chains and along the chains to compare the in-phase and out-of-phase permittivities throughout the temperature and frequency range studied.
Abstract: Certain molecular solids, especially polymeric ones, can exhibit high dielectric constants and electronic conductivity. They are normally non-crystalline. The highly conjugated polymer chosen for this study is representative of a large class of similar highly stable, carrier rich, organic solids. Dielectric constants of 5000 and higher were observed. Conductivity and permittivity were studied over a range of frequencies (dc to 300 kHz) and temperatures (68.5 to 296°K). The dc conduction is electronic, with an activation energy of 0.095 eV. The ac conduction follows a T 1 4 relation, and increases with frequency. Transport is by thermally assisted hopping (tunneling) between chains and along the chains. Thermally activated motion of the carriers within the chains was followed by comparing the in-phase and out-of-phase permittivities throughout the temperature and frequency range studied.
15 citations
TL;DR: In this paper, electron and hole transport in S α and Se α is compared on the basis of the available drift mobility data and it is concluded that in both crystals holes propagate in a band with a lattice mobility of about 10 cm 2 s −1 V −1.
15 citations
TL;DR: In this paper, a quantum lattice dynamics treatment for the angular degrees of freedom in molecular solids is presented for the quadrupole forces in solid hydrogen, nitrogen and carbon dioxide.
11 citations
TL;DR: In this paper, the authors used a quantum crystal formalism to resolve the large discrepancy between the experimental equation of state and several recent theories in the solid phase at high pressure, which does not require the introduction of any new intermolecular potential.
5 citations
TL;DR: Spin-lattice relaxation time studies are reported of protons in the molecular solids: aniline, N-methylaniline and 2,5-dimethyleniline.
Abstract: Spin-lattice relaxation time studies are reported of protons in the molecular solids: aniline, N-methylaniline, NN-dimethylaniline and 2,5-dimethylaniline The temperature dependence of the relaxation times T1 and T1ρ are interpreted in terms of the possible hindered motions occurring in the lattice The restricting potential barriers are deduced and compared with those derived from dielectric studies Some new thermal data are also presented
3 citations
3 citations
TL;DR: In this article, the importance of nuclear permutation symmetry in solids composed of polyatomic molecules is reviewed and various methods of measuring tunnelling frequencies are reviewed and proposed, and some basic relationships between nuclear spin symmetry and quantum mechanical tunneling in polyatomic solids are discussed.
Abstract: The small amount of experimental evidence indicating the importance of nuclear permutation symmetry in solids composed of polyatomic molecules is reviewed. In the case of methane and its deuterated modifications, heat capacity, spectroscopic and nmr measurements have each played an important role, while in solids having CH3 groups the only significant experiments have involved nmr. Some basic relationships between nuclear spin symmetry and quantum mechanical tunnelling in solids are discussed and various methods of measuring tunnelling frequencies are reviewed and proposed.
2 citations