Extended BEG model of monhalogenated methanes physisorbed on ionic crystals

Abstract

The 2D dielectric phases and phase transitions of adsorbed dipolar molecules are modeled using a dilute spin-one Ising model. This model is studied in the Blume-Emery-Griffiths formalism, using a mean-field approximation, where the interaction parameters are related to system interaction energies using a unique averaging procedure. The model is applied to four halogenated methane species physisorbed on MgO(100) and NaCl(100) surfaces using previous experimental and theoretical studies to estimate the interaction energy parameters. We find that temperature-and coverage-dependent antiferroelectric to ferroelectric, coverage-dependant ferroelectric up to ferroelectric down, reentrant ferroelectric to ferroelectric, and order-disorder dipole phase transitions can occur. Phase diagrams based on this model are presented.

Dynamic interfaces in an organic thin film

“…1, should impose a substantial difference in the behavior of the S and CE edge boundaries. Thus the similarity of the measured thermodynamic and kinetic values, specifically the step stiffness and mobility listed in Table I, for these two boundaries is initially quite surprising, and has very interesting physical consequences (4,36,37). Here we will derive a specific model for the interactions between ACA molecules, modeled as pairwise interactions within a lattice gas framework, and test the model's ability to reproduce the experimentally measured edge free energies (stiffnesses).…”

“…5) or D ("down" shown as blue/medium gray). This leads to a three-component (U, D, and vacancy) lattice gas that maps onto an anisotropic version of the Blume, Emery, Griffiths (BEG) or spin 1 Ising model (36,37). There have been many studies (36) of different versions of the BEG model in other contexts, though not with parameters expressing the competition between anisotropic bonding (intermolecular) and substrate (single particle field) terms needed here.…”

Phase transitions in a two-dimensional lattice gas model of orientable diatomic molecules. II. Order-disorder transitions of superantiferromagnetic andc(2×2)AFphases

“…[4][5][6]20,21 The model proposed by Blume, Emery, and Griffiths ͑BEG͒ 13 was quite successfully used to describe the phase behavior of liquid helium mixtures, consisting of 3 He and 4 He isotopes.…”

CH3Br Structures on Pt(111): Kinetically Controlled Self-Assembly of Weakly Adsorbed Dipolar Molecules

“…The ability to flip the orientation of adsorbed CH 3 Br as a function of O coverage on O/Ru(001) surfaces has enabled fundamental studies of the steric effect in the dissociative electron attachment of electrons to an adsorbate (i.e., the electron/ molecule approach geometry is important). , Helium beam scattering indicates that CH 3 Br antiferroelectrically orders on C(0001) graphite, NaCl(001), and LiF(001) surfaces . Theoretical analysis of the surface ordering of dipolar molecules, such as CH 3 Br on MgO, indicates a variety of ordered antiferroelectric, ferroelectric, and disordered phases are possible for different values of the coverage, temperature, adsorbate binding energy, and dipole moment. Understanding 2-D dielectric ordering behavior is also deemed important to the development of next generation nonvolatile memory and electronic devices based on ferroelectric thin films. , …”

“…14,19 Helium beam scattering indicates that CH 3 Br antiferroelectrically orders on C(0001) graphite, NaCl(001), and LiF(001) surfaces. 16 Theoretical analysis of the surface ordering of dipolar molecules, such as CH 3 Br on MgO, 20 indicates a variety of ordered antiferroelectric, ferroelectric, and disordered phases are possible for different values of the coverage, temperature, adsorbate binding energy, and dipole moment. Understanding 2-D dielectric ordering behavior is also deemed important to the development of next generation nonvolatile memory and electronic devices based on ferroelectric thin films.…”