Lattice dynamics and phase transition of acetylene

The phonon dispersion curves of cubic acetylene, tetragonal urea, and monoclinic sodium carbonate are calculated from the generic force field using the direct method. The force constants of the dynamical matrix are determined from the forces induced by the displacement of an atom in the simulated supercell. The obtained dispersion curves are displayed along many high-symmetry lines of the Brillouin zone. For sodium carbonate, a soft mode has been found. The dispersion curves of urea fit quite well to the measured phonons. The results show that the force field approach leads to reasonable description of the lattice dynamics of crystals.

show abstract

“…The qualitative agreement with our curves is reasonable; however, quantitatively our frequency modes are a little higher than those of Ref. 24.…”

Section: A Acetylene C 2 Hsupporting

confidence: 60%

Calculations of the phonon dispersion curves of C2H2, OC(ND2)2, and Na2CO3 from generic force field

Parliński

Chapuis

1999

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…Therefore, higher order electric moments are needed to describe the electrostatic portion of the intermolecular potential of C 2 H 2 . [14][15][16] When these are included, the optimized geometry is based upon the donor-acceptor interaction between a C 2 H 2 carboncarbon triple-bond and a C 2 H 2 hydrogen. This is clearly seen in the orthorhombic primitive unit cell which consists of two C 2 H 2 molecules arranged in a T-shape.…”

Section: Introductionmentioning

confidence: 99%

Infrared spectroscopy and modeling of co-crystalline CO2·C2H2 aerosol particles. II. The structure and shape of co-crystalline CO2·C2H2 aerosol particles

Preston

Signorell

2012

The Journal of Chemical Physics

View full text Add to dashboard Cite

Infrared absorption spectra of co-crystalline CO(2)·C(2)H(2) aerosol particles were modeled using a combination of two methods. Density functional theory was used to model several bulk CO(2)·C(2)H(2) co-crystal structures and to calculate their lattice energies and frequency-dependent dielectric tensors. This was necessary as there currently exists no crystallographic or refractive index data on co-crystalline CO(2)·C(2)H(2)due to its metastability. The discrete dipole approximation was then used to calculate infrared absorption spectra of different model particles using the dielectric tensors calculated using density functional theory. Results from these simulations were compared to the experimental spectrum of co-crystalline CO(2)·C(2)H(2) aerosol particles. The aerosol particles after the decomposition of the co-crystalline phase were studied in Part I.

show abstract

“…Lattice-dynamical calculations using Coulombic interactions have been reported, especially for small molecules (Rastogi, Anderson & Leech, 1979;Gamba & Bonadeo, 1982) where experimental dipole or quadrupole moments are known and facilitate the adoption of an electrostatic potential model. Nevertheless, for large molecules a multipolar expansion is slowly convergent and higher-order multipoles are not normally known experimentally.…”

Section: Introductionmentioning

confidence: 99%

The influence of Coulombic interactions on thermal parameters for naphthalene and anthracene: a lattice-dynamical approach

Criado¹

1989

Acta Cryst Sect A

View full text Add to dashboard Cite

A lattice-dynamical calculation of thermal parameters is performed for naphthalene and anthracene in the external Born-von Karman formalism using 6-exp potential functions and electrostatic interactions in the form of an atomic point-charge model. Phonon dispersion curves and density-of-states functions are calculated with and without charges. In general, the effect of the Coulombic forces is small and sensibly affects optical branches linked to the Bu mode in both compounds, improving the agreement with the experimental data. The effect on thermal parameters is roughly opposite to that of molecular non-rigidity.

show abstract

Lattice dynamics and phase transition of acetylene

Cited by 33 publications

References 26 publications

Calculations of the phonon dispersion curves of C2H2, OC(ND2)2, and Na2CO3 from generic force field

Calculations of the phonon dispersion curves of C2H2, OC(ND2)2, and Na2CO3 from generic force field

Infrared spectroscopy and modeling of co-crystalline CO2·C2H2 aerosol particles. II. The structure and shape of co-crystalline CO2·C2H2 aerosol particles

The influence of Coulombic interactions on thermal parameters for naphthalene and anthracene: a lattice-dynamical approach

Contact Info

Product

Resources

About