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Full-Text Articles in Physics

Investigation Of Major Intermolecular Interactions In 7,8-Dihydrobenzo(K)Phenanthridin-6(5h)-One Crystal Using Quantum Calculations And Crystallographic Visualization Programs, Zhiwei Liao, Tonglei Li, Mingtao Zhang Oct 2013

Investigation Of Major Intermolecular Interactions In 7,8-Dihydrobenzo(K)Phenanthridin-6(5h)-One Crystal Using Quantum Calculations And Crystallographic Visualization Programs, Zhiwei Liao, Tonglei Li, Mingtao Zhang

The Summer Undergraduate Research Fellowship (SURF) Symposium

Currently, tablets and capsules are the most common ways of delivering drugs. The active pharmaceutical ingredients and excipients used to make those tablets and capsules are in their crystalline form generally. However, a single molecule can form multiple different crystal structures because of different packing arrangements of the molecules. These different crystal structures have identical chemical composition but different properties such as solubility, density, stability, etc. This phenomenon is called polymorphism. Occurrence of polymorphism could be a disaster for both patients and pharmaceutical companies, as the drug could lose its efficacy due to changes in properties. Studying intermolecular interactions in ...


A Six-Dimensional H2–H2 Potential Energy Surface For Bound State Spectroscopy, Robert Hinde Jan 2008

A Six-Dimensional H2–H2 Potential Energy Surface For Bound State Spectroscopy, Robert Hinde

Chemistry Publications and Other Works

We present a six-dimensional potential energy surface for the (H2)2 dimer based on coupled-cluster electronic structure calculations employing large atom-centered Gaussian basis sets and a small set of midbond functions at the dimer’s center of mass. The surface is intended to describe accurately the bound and quasibound states of the dimers (H2)2, (D2)2, and H2–D2 that correlate with H2 or D2 monomers in the rovibrational levels (v, j) =(0,0), (0,2), (1,0), and (1,2). We employ a close-coupled approach to compute the energies of these ...


Three-Body Interactions In Solid Parahydrogen, Robert Hinde Dec 2007

Three-Body Interactions In Solid Parahydrogen, Robert Hinde

Robert Hinde

We use coupled-cluster ab initio methods to evaluate the non-pairwise-additive interactions in clusters of three parahydrogen (pH2) molecules. For acute triangular (pH2)3 geometries that play a prominent role in solid pH2, these interactions lower substantially the trimer’s total interaction energy. Our findings suggest that a widely-used effective pair potential for solid pH2 derives its accuracy from a fortuitous cancellation of errors at small intermolecular distances.


Interaction-Induced Dipole Moment Of The Ar–H2 Dimer: Dependence On The H2 Bond Length, Robert J. Hinde Jan 2006

Interaction-Induced Dipole Moment Of The Ar–H2 Dimer: Dependence On The H2 Bond Length, Robert J. Hinde

Chemistry Publications and Other Works

We present ab initio calculations of the interaction-induced dipole moment of the Ar–H2 van der Waals dimer. The primary focus of our calculations is on the H2 bond length dependence of the dipole moment, which determines the intensities of both the collision-induced H2 = 1 ← 0 fundamental band in gaseous Ar–H2 mixtures and the dopant-induced H2 = 1 ← 0 absorption feature in Ar-doped solid H2 matrices. Our calculations employ large atom-centered basis sets, diffuse bond functions positioned between the two monomers, and a coupled cluster treatment of valence electron correlation; core-valence correlation effects appear ...


Dependence Of The H2–H2 Interaction On The Monomer Bond Lengths: Steps Toward An Accurate Ab Initio Estimate, Robert Hinde Dec 2005

Dependence Of The H2–H2 Interaction On The Monomer Bond Lengths: Steps Toward An Accurate Ab Initio Estimate, Robert Hinde

Robert Hinde

We compute the vibrational coupling between two H2 molecules from ab initio quantum chemical calculations of the H2–H2 potential carried out at the full configuration interaction level of theory using the atom-centered aug-cc-pVTZ basis set for hydrogen. We compare the full configuration interaction results with those obtained using two variants of coupled cluster theory and find that a fully iterative treatment of connected triples may be required to estimate the H2–H2 vibrational coupling accurately using coupled cluster theory.


Interaction-Induced Dipole Moment Of The Ar–H2 Dimer: Dependence On The H2 Bond Length, Robert J. Hinde Dec 2005

Interaction-Induced Dipole Moment Of The Ar–H2 Dimer: Dependence On The H2 Bond Length, Robert J. Hinde

Robert Hinde

We present ab initio calculations of the interaction-induced dipole moment of the Ar–H2 van der Waals dimer. The primary focus of our calculations is on the H2 bond length dependence of the dipole moment, which determines the intensities of both the collision-induced H2 = 1 ← 0 fundamental band in gaseous Ar–H2 mixtures and the dopant-induced H2 = 1 ← 0 absorption feature in Ar-doped solid H2 matrices. Our calculations employ large atom-centered basis sets, diffuse bond functions positioned between the two monomers, and a coupled cluster treatment of valence electron correlation; core-valence correlation effects appear ...


Vibrational Dependence Of The H2–H2 C6 Coefficients, Robert Hinde Jan 2005

Vibrational Dependence Of The H2–H2 C6 Coefficients, Robert Hinde

Chemistry Publications and Other Works

We use the sum-over-states formalism to compute the imaginary-frequency dipole polarizabilities for H2, as a function of the H–H bond length, at the full configuration interaction level of theory using atom-centered d-aug-cc-pVQZ basis sets. From these polarizabilities, we obtain isotropic and anisotropic C6 dispersion coefficients for a pair of H2 molecules as functions of the two molecules’ bond lengths.


Vibrational Dependence Of The H2–H2 C6 Coefficients, Robert Hinde Dec 2004

Vibrational Dependence Of The H2–H2 C6 Coefficients, Robert Hinde

Robert Hinde

We use the sum-over-states formalism to compute the imaginary-frequency dipole polarizabilities for H2, as a function of the H–H bond length, at the full configuration interaction level of theory using atom-centered d-aug-cc-pVQZ basis sets. From these polarizabilities, we obtain isotropic and anisotropic C6 dispersion coefficients for a pair of H2 molecules as functions of the two molecules’ bond lengths.


The He-Lih Potential Energy Surface Revisited. I. An Interpolated Rigid Rotor Surface, Robert Hinde Jan 1999

The He-Lih Potential Energy Surface Revisited. I. An Interpolated Rigid Rotor Surface, Robert Hinde

Chemistry Publications and Other Works

We reconsider the potential energy surface of the He–LiH system recently examined by Gianturco and co-workers [F. A. Gianturco et al., Chem. Phys. 215, 227 (1997)]. We compute the He–LiH interaction energy at the CCSD(T) level using large correlation consistent atomic basis sets supplemented with bond functions. To capture the severe anisotropy of the He–LiH potential, we interpolate our ab initio points in the angular direction with cubic splines, then expand the splines in terms of Legendre polynomials. The resulting smooth potential surface differs substantially from that of Gianturco et al.; in particular, our attractive He ...


The He-Lih Potential Energy Surface Revisited. I. An Interpolated Rigid Rotor Surface, Robert Hinde Dec 1998

The He-Lih Potential Energy Surface Revisited. I. An Interpolated Rigid Rotor Surface, Robert Hinde

Robert Hinde

We reconsider the potential energy surface of the He–LiH system recently examined by Gianturco and co-workers [F. A. Gianturco et al., Chem. Phys. 215, 227 (1997)]. We compute the He–LiH interaction energy at the CCSD(T) level using large correlation consistent atomic basis sets supplemented with bond functions. To capture the severe anisotropy of the He–LiH potential, we interpolate our ab initio points in the angular direction with cubic splines, then expand the splines in terms of Legendre polynomials. The resulting smooth potential surface differs substantially from that of Gianturco et al.; in particular, our attractive He ...