Hemali Davande | University of Utah (original) (raw)

Papers by Hemali Davande

Research paper thumbnail of Ag nanowire based transparent conductor for CIGS PV

Coated silver nanowires (AgNW) have been considered as a replacement for transparent conducting o... more Coated silver nanowires (AgNW) have been considered as a replacement for transparent conducting oxides (TCOs) in CIGS based photovoltaic devices. The advantages of AgNW over TCOs are discussed, and optical and electrical characteristics of AgNWs on glass are presented. Similarly fabricated AgNWs with varying sheet resistance on CIGS devices were tested against ITO transparent conductor controls. The CIGS was produced

Research paper thumbnail of Ag Nanowire Based Transparent Conductor for CIGS PV

Coated silver nanowires (AgNW) have been considered as a replacement for transparent conducting o... more Coated silver nanowires (AgNW) have been considered as a replacement for transparent conducting oxides (TCOs) in CIGS based photovoltaic devices. The advantages of AgNW over TCOs are discussed, and optical and electrical characteristics of AgNWs on glass are presented. Similarly fabricated AgNWs with varying sheet resistance on CIGS devices were tested against ITO transparent conductor controls. The CIGS was produced

Research paper thumbnail of Quantum Chemistry–Based Force Field for Simulations of Energetic Dinitro Compounds

Journal of Energetic Materials, 2005

A quantum chemistry-based force field for molecular dynamics simulations of energetic dinitro com... more A quantum chemistry-based force field for molecular dynamics simulations of energetic dinitro compounds has been developed, based on intermolecular binding energies, molecular geometries, molecular electrostatic potentials, and conformational energies obtained from quantum chemistry calculations on model compounds. Nonbonded parameters were determined by fitting experimental densities and heats of vaporizations of model compounds. Torsional parameters were parameterized to reproduce accurately the relative conformational energy minima and barriers in 2, 2-dinitropropane, di-methoxy di-methyl ether, 2,2-dinitro-3-methoxypropane, and bis(2,2-dinitropropyl)formal. Molecular dynamics simulations using the developed force field accurately reproduce thermodynamic and transport properties of 1,1-dinitroethane, 2,2-dinitropropane, and a eutectic mixture of bis (2,2dinitropropyl)formal and bis (2,2-dinitropropyl)acetal.

Research paper thumbnail of Linear Viscoelastic Response of PBX9501 Binder using Molecular Dynamics Simulations

Quantum-chemistry based force fields for Estane, bis-dinitropropyl formal (BDNPF) and bis dinitro... more Quantum-chemistry based force fields for Estane, bis-dinitropropyl formal (BDNPF) and bis dinitropropyl acetal (BDNPA) plasticizer have been developed, validated and utilized in atomistic molecular dynamics (MD) simulations of a model PBX-9501 binder. The viscoelastic response of unentangled binder melt using MD simulations was studied. These results were then used in prediction of linear viscoelastic response of an entangled melt using theoretical models for viscoelastic response of block copolymers and compared with experiments.

Research paper thumbnail of A Molecular Dynamics Simulation Study of C 60 Fullerenes Inside a Dimyristoylphosphatidylcholine Lipid Bilayer

Journal of Physical Chemistry B, 2007

We have carried out atomistic molecular dynamics simulations of C60 fullerenes inside a dimyristo... more We have carried out atomistic molecular dynamics simulations of C60 fullerenes inside a dimyristoylphosphatidylcholine lipid bilayer and an alkane melt. Simulations reveal that the preferred position of a single C60 fullerene is about 6-7 A off of the center plane, allowing the fullerene to take advantage of strong dispersion interactions with denser regions of the bilayer. Further displacement (>8 A) of the fullerene away from the center plane results in a rapid increase in free energy likely due to distortion of the lipid head group layer. The effective interaction between fullerenes (direct interaction plus environment (bilayer)-induced interaction), measured as the potential of mean force (POMF) between two fullerenes as a function of their separation, was found to be significantly less attractive in the lipid bilayer than in an alkane melt of the same molecular weight as the lipid tails. Only part of this difference can be accounted for by the more favorable interaction of the fullerene with the relatively denser bilayer. Additionally, our POMF studies indicate that the bilayer is less able to accommodate the larger aggregated fullerene pair than isolated single fullerenes, again likely due to distortion of the bilayer structure. The implications of these effects on aggregation of fullerenes within lipid bilayer are considered.

Research paper thumbnail of Passive Transport of C 60 Fullerenes through a Lipid Membrane: A Molecular Dynamics Simulation Study

Journal of Physical Chemistry B, 2008

To investigate the implications of the unique properties of fullerenes on their interaction with ... more To investigate the implications of the unique properties of fullerenes on their interaction with and passive transport into lipid membranes, atomistic molecular dynamics simulations of a C60 fullerene in a fully hydrated di-myristoyl-phoshatidylcholine lipid membrane have been carried out. In these simulations the free energy and the diffusivity of the fullerene were obtained as a function of its position within the membrane. These properties were utilized to calculate the permeability of fullerenes through the lipid membrane. Simulations reveal that the free energy decreases as the fullerene passes from the aqueous phase, through the head group layer and into the hydrophobic core of the membrane. This decrease in free energy is not due to hydrophobic interactions but rather to stronger van der Waals (dispersion) interactions between the fullerene and the membrane compared to those between the fullerene and (bulk) water. It was found that there is no free energy barrier for transport of a fullerene from the aqueous phase into the lipid core of the membrane. In combination with strong partitioning of the fullerenes into the lipidic core of the membrane, this "barrierless" penetration results in an astonishingly large permeability of fullerenes through the lipid membrane, greater than observed for any other known penetrant. When the strength of the dispersion interactions between the fullerene and its surroundings is reduced in the simulations, thereby emulating a nanometer sized hydrophobic particle, a large free energy barrier for penetration of the head group layer emerges, indicating that the large permeability of fullerenes through lipid membranes is a result of their unique interaction with their surrounding medium.

Research paper thumbnail of Thermodynamic, Transport, and Viscoelastic Properties of PBX9501 Binder: A Molecular Dynamics Simulations Study

Journal of Energetic Materials, 2008

Atomistic molecular dynamics simulations were performed on a low-molecular-weight nitroplasticize... more Atomistic molecular dynamics simulations were performed on a low-molecular-weight nitroplasticized Estane® mixture representative of the binder used in PBX-9501. Pressure-volume-temperature (PVT) behavior over a wide range of pressures and temperatures above the order-disorder temperature (ODT) of Estane was determined and represented with the empirical Tait and Sun equations of state. The effect of temperature, pressure, and plasticization on transport properties

Research paper thumbnail of Ag nanowire based transparent conductor for CIGS PV

Coated silver nanowires (AgNW) have been considered as a replacement for transparent conducting o... more Coated silver nanowires (AgNW) have been considered as a replacement for transparent conducting oxides (TCOs) in CIGS based photovoltaic devices. The advantages of AgNW over TCOs are discussed, and optical and electrical characteristics of AgNWs on glass are presented. Similarly fabricated AgNWs with varying sheet resistance on CIGS devices were tested against ITO transparent conductor controls. The CIGS was produced

Research paper thumbnail of Ag Nanowire Based Transparent Conductor for CIGS PV

Coated silver nanowires (AgNW) have been considered as a replacement for transparent conducting o... more Coated silver nanowires (AgNW) have been considered as a replacement for transparent conducting oxides (TCOs) in CIGS based photovoltaic devices. The advantages of AgNW over TCOs are discussed, and optical and electrical characteristics of AgNWs on glass are presented. Similarly fabricated AgNWs with varying sheet resistance on CIGS devices were tested against ITO transparent conductor controls. The CIGS was produced

Research paper thumbnail of Quantum Chemistry–Based Force Field for Simulations of Energetic Dinitro Compounds

Journal of Energetic Materials, 2005

A quantum chemistry-based force field for molecular dynamics simulations of energetic dinitro com... more A quantum chemistry-based force field for molecular dynamics simulations of energetic dinitro compounds has been developed, based on intermolecular binding energies, molecular geometries, molecular electrostatic potentials, and conformational energies obtained from quantum chemistry calculations on model compounds. Nonbonded parameters were determined by fitting experimental densities and heats of vaporizations of model compounds. Torsional parameters were parameterized to reproduce accurately the relative conformational energy minima and barriers in 2, 2-dinitropropane, di-methoxy di-methyl ether, 2,2-dinitro-3-methoxypropane, and bis(2,2-dinitropropyl)formal. Molecular dynamics simulations using the developed force field accurately reproduce thermodynamic and transport properties of 1,1-dinitroethane, 2,2-dinitropropane, and a eutectic mixture of bis (2,2dinitropropyl)formal and bis (2,2-dinitropropyl)acetal.

Research paper thumbnail of Linear Viscoelastic Response of PBX9501 Binder using Molecular Dynamics Simulations

Quantum-chemistry based force fields for Estane, bis-dinitropropyl formal (BDNPF) and bis dinitro... more Quantum-chemistry based force fields for Estane, bis-dinitropropyl formal (BDNPF) and bis dinitropropyl acetal (BDNPA) plasticizer have been developed, validated and utilized in atomistic molecular dynamics (MD) simulations of a model PBX-9501 binder. The viscoelastic response of unentangled binder melt using MD simulations was studied. These results were then used in prediction of linear viscoelastic response of an entangled melt using theoretical models for viscoelastic response of block copolymers and compared with experiments.

Research paper thumbnail of A Molecular Dynamics Simulation Study of C 60 Fullerenes Inside a Dimyristoylphosphatidylcholine Lipid Bilayer

Journal of Physical Chemistry B, 2007

We have carried out atomistic molecular dynamics simulations of C60 fullerenes inside a dimyristo... more We have carried out atomistic molecular dynamics simulations of C60 fullerenes inside a dimyristoylphosphatidylcholine lipid bilayer and an alkane melt. Simulations reveal that the preferred position of a single C60 fullerene is about 6-7 A off of the center plane, allowing the fullerene to take advantage of strong dispersion interactions with denser regions of the bilayer. Further displacement (>8 A) of the fullerene away from the center plane results in a rapid increase in free energy likely due to distortion of the lipid head group layer. The effective interaction between fullerenes (direct interaction plus environment (bilayer)-induced interaction), measured as the potential of mean force (POMF) between two fullerenes as a function of their separation, was found to be significantly less attractive in the lipid bilayer than in an alkane melt of the same molecular weight as the lipid tails. Only part of this difference can be accounted for by the more favorable interaction of the fullerene with the relatively denser bilayer. Additionally, our POMF studies indicate that the bilayer is less able to accommodate the larger aggregated fullerene pair than isolated single fullerenes, again likely due to distortion of the bilayer structure. The implications of these effects on aggregation of fullerenes within lipid bilayer are considered.

Research paper thumbnail of Passive Transport of C 60 Fullerenes through a Lipid Membrane: A Molecular Dynamics Simulation Study

Journal of Physical Chemistry B, 2008

To investigate the implications of the unique properties of fullerenes on their interaction with ... more To investigate the implications of the unique properties of fullerenes on their interaction with and passive transport into lipid membranes, atomistic molecular dynamics simulations of a C60 fullerene in a fully hydrated di-myristoyl-phoshatidylcholine lipid membrane have been carried out. In these simulations the free energy and the diffusivity of the fullerene were obtained as a function of its position within the membrane. These properties were utilized to calculate the permeability of fullerenes through the lipid membrane. Simulations reveal that the free energy decreases as the fullerene passes from the aqueous phase, through the head group layer and into the hydrophobic core of the membrane. This decrease in free energy is not due to hydrophobic interactions but rather to stronger van der Waals (dispersion) interactions between the fullerene and the membrane compared to those between the fullerene and (bulk) water. It was found that there is no free energy barrier for transport of a fullerene from the aqueous phase into the lipid core of the membrane. In combination with strong partitioning of the fullerenes into the lipidic core of the membrane, this "barrierless" penetration results in an astonishingly large permeability of fullerenes through the lipid membrane, greater than observed for any other known penetrant. When the strength of the dispersion interactions between the fullerene and its surroundings is reduced in the simulations, thereby emulating a nanometer sized hydrophobic particle, a large free energy barrier for penetration of the head group layer emerges, indicating that the large permeability of fullerenes through lipid membranes is a result of their unique interaction with their surrounding medium.

Research paper thumbnail of Thermodynamic, Transport, and Viscoelastic Properties of PBX9501 Binder: A Molecular Dynamics Simulations Study

Journal of Energetic Materials, 2008

Atomistic molecular dynamics simulations were performed on a low-molecular-weight nitroplasticize... more Atomistic molecular dynamics simulations were performed on a low-molecular-weight nitroplasticized Estane® mixture representative of the binder used in PBX-9501. Pressure-volume-temperature (PVT) behavior over a wide range of pressures and temperatures above the order-disorder temperature (ODT) of Estane was determined and represented with the empirical Tait and Sun equations of state. The effect of temperature, pressure, and plasticization on transport properties