Values Of Internal Energy Research Articles

Density functional theory (DFT) based study of solvent effect on B10N11 and B10N11H7 (Gly)2 nano structures

In this present work, all calculations were carried out with the Gaussian 98 program based on density functional theory (DFT) at B3LYP/3-21G level of theory. Then stability and grand state of B10N11 and B10N11H7 (Gly)2 nanocones in bulk and different solvents were investigated. It is clear that solvent effects were reviewed with concentration on quantitative values of Gibbs free energy, enthalpy, internal energy and dipole moment in the spread of solvents around these two nano structures and temperature effect was studied on the stability of these novel structures in the same solvents. Furthermore we compared the results of gas phase and different solvents when surrounding these two nano structures. In this work, NMR shielding parameters were calculated based on each atom to recognize active sites in these two systems. The results showed that because of high stability of B10N11 and B10N11H7 (Gly)2, these novel structures could be the best candidates and most favorable in biological systems and drug delivery.

Molecular Dynamics Approaches Estimate the Binding Energy of HIV-1 Integrase Inhibitors and Correlate with In Vitro Activity

The design of novel integrase (IN) inhibitors has been aided by recent crystal structures revealing the binding mode of these compounds with a full-length prototype foamy virus (PFV) IN and synthetic viral DNA ends. Earlier docking studies relied on incomplete structures and did not include the contribution of the viral DNA to inhibitor binding. Using the structure of PFV IN as the starting point, we generated a model of the corresponding HIV-1 complex and developed a molecular dynamics (MD)-based approach that correlates with the in vitro activities of novel compounds. Four well-characterized compounds (raltegravir, elvitegravir, MK-0536, and dolutegravir) were used as a training set, and the data for their in vitro activity against the Y143R, N155H, and G140S/Q148H mutants were used in addition to the wild-type (WT) IN data. Three additional compounds were docked into the IN-DNA complex model and subjected to MD simulations. All three gave interaction potentials within 1 standard deviation of values estimated from the training set, and the most active compound was identified. Additional MD analysis of the raltegravir- and dolutegravir-bound complexes gave internal and interaction energy values that closely match the experimental binding energy of a compound related to raltegravir that has similar activity. These approaches can be used to gain a deeper understanding of the interactions of the inhibitors with the HIV-1 intasome and to identify promising scaffolds for novel integrase inhibitors, in particular, compounds that retain activity against a range of drug-resistant mutants, making it possible to streamline synthesis and testing.

Comparative research for transmission-mode GaAs photocathodes of different doping structures on surface photovoltage

In order to well study the internal body performance for transmission-mode GaAs photocathode of different varied doping structures, two GaAs photocathodes of exponential doping structure and gradient doping structure were designed respectively. Because surface photovoltage spectrum has close relation with the internal properties of GaAs photocathodes, the connection between surface photovoltage and internal electronic field was well discussed through deduction and calculation. The difference of two structures and the value of internal electronic energy were exactly calculated and verified by experiments. The internal band bending energy could form an internal electronic field with the same direction, which could help the photo-excited electrons to move toward surface barrier layer. This research shows a better method to well study the varied doping structures for GaAs photocathode materials and will help to improve the growth structure for transmission-mode GaAs photocathode module in the future.

Structural variability and dynamics of the P3HT/PCBM interface and its effects on the electronic structure and the charge-transfer rates in solar cells

Using a range of realistic interface geometries obtained from a molecular dynamics simulation we study the effects of different microscopic atomic arrangements on the electronic structure and charge transfer rates of the prototypical photovoltaic interface between P3HT (poly(3-hexylthiophene)) and PCBM ([6,6]-phenyl-C(61)-butyric acid methyl ester). The electronic structures of charge-transfer (CT) states belong to two groups that can be denoted as "charge-separated" and "charge-bridging" states. For the former group of structures, which may lead to fully separated charges, the ranges and the average values of internal reorganization energy, the electronic coupling and the charge separated states energy are evaluated. A range and distribution of absolute charge separation (CS) and recombination (CR) rates are computed using the Marcus-Levich-Jortner rate equation. Due to the variety of P3HT/PCBM interface structures, a very broad range of CS (7.7 × 10(9)-1.8 × 10(12) s(-1)) and CR (2.5 × 10(5)-1.1 × 10(10) s(-1)) "instantaneous" rates are computed. However, the energetic parameters affecting the rate evolve in time due to the dynamic nature of the interface with a characteristic timescale of about 10 ns. For this reason the slowest CR instantaneous rates are not observed and the minimum CR rate observed is determined by the rate of conformational rearrangement at the interface. The combination of these observations provides a more general framework for the interpretation of experimental spectroscopic data, suggesting that the analysis based on simple first order rates may be insufficient to describe charge transfer in organic solar cell interfaces.

High-Energy Fragmentation in Nanophotonic Ion Production by Laser-Induced Silicon Microcolumn Arrays

Laser-induced silicon microcolumn arrays (LISMA) exhibit nanophotonic ion production in laser desorption ionization experiments (Walker et al., Angew. Chem., Int. Ed. 2009, 48, 1669) for small-to-medium-size molecules. Although these surfaces are known to promote fragmentation of adsorbates at high laser fluences, the nature, extent, and origin of peptide ion decomposition remains unknown. Here we demonstrate that peptide ions, e.g., bradykinin, leucine enkephalin, angiotensin I, substance P, and various tripeptides, desorbed from these substrates show an increasing degree of fragmentation as the fluence is raised. Compared to other ion fragmentation methods, LISMA shows similarity to high-energy collision activated dissociation (CAD), ion decomposition produced by metastable atom beams, and surface induced dissociation (SID). While some of the produced fragments are associated with high-energy decomposition channels, for example, the abundant a5 fragment produced from singly protonated bradykinin ion, other ions in the same spectra (e.g., the ammonia loss from the protonated bradykinin ion) are predominantly produced by low energy processes. To explore the role of internal energy in the fragmentation of ions produced from LISMA, the survival yields of eight benzyl-substituted benzylpyridinium thermometer ions were also studied as a function of laser fluence and surface derivatization. The corresponding internal energies were determined using the Rice−Ramsperger−Kassel−Marcus formalism. On both native and silane-derivatized surfaces, the thermometer ions showed stable internal energy values over a wide range of laser fluences. This presented a strong contrast to the behavior of the peptides that yielded high-energy fragments at increased fluence. As the thermometer ions did not record an increase in internal energy, the enhanced fragmentation of the peptides was indicative of alternative high-energy mechanisms.

Electrical conductivity of carbon plasma

The electrical conductivity of carbon plasmas is measured in the range of densities from about 0.6 solid density down to about 0.05 solid density, and reported for values of internal energy ranging from 2 to 22 kJ/gm . Plasmas are formed by rapid electrical discharge through thin graphite fibers immersed in a water bath. The pressure in the expanding plasma column is determined by use of a hydrodynamic model to describe the effect on the water surround. It is found that at constant internal energy per unit mass U, conductivity sigma varies with specific volume v as sigma = v(-alpha), where alpha is about 1 for U < 6 kJ gm , and rises to about 1.5 for U = 22 kJ gm .

Solution of the isochoric–isoenergetic flash problem by direct entropy maximization

A new algorithm to find the phase equilibrium conditions in systems with specified values of internal energy, volume, and number of moles of each component present (isochoric–isoenergetic flash problem) is proposed. The core of the procedure consists of maximizing the system entropy by iterating on the values, in each phase, of internal energy, volume, and number of moles of each component. Analytical expressions for the physical properties and derivatives required by the calculations were generated by computer algebra. The algorithm tests for the possible need to add or remove phases during the course of iterations. The paper discusses possible numerical difficulties during application of the procedure and how to overcome them. The algorithm has shown to be robust and capable of solving multiphase equilibrium problems, avoiding trivial solutions.

Improved radial distribution functions for Coulomb charged fluid based on first-order mean spherical approximation

In this work, we solve the Ornstein-Zernike equation in a simple, analytical, and consistent manner to obtain the like and unlike radial distribution functions (RDFs) for charged fluids. To improve mean spherical approximation (MSA) solutions, the direct correlation functions both for the density and charge contributions are modified with the Yukawa potential, respectively. On the basis of the contact values of RDFs and excess internal energy of the system, we construct correlated equations to cope with the potential parameters. Thus obtained equations are solved with the first-order MSA method. The resulting like and unlike RDFs are in good agreement with molecular simulation data within a wide range of densities and temperatures.

Internal energy distribution of peptides in electrospray ionization : ESI and collision‐induced dissociation spectra calculation

The internal energy of ions and the timescale play fundamental roles in mass spectrometry. The main objective of this study is to estimate and compare the internal energy distributions of different ions (different nature, degree of freedom 'DOF' and fragmentations) produced in an electrospray source (ESI) of a triple-quadrupole instrument (Quattro I Micromass). These measurements were performed using both the Survival Yield method (as proposed by De Pauw) and the MassKinetics software (kinetic model introduced by Vékey). The internal energy calibration is the preliminary step for ESI and collision-induced dissociation (CID) spectra calculation. meta-Methyl-benzylpyridinium ion and four protonated peptides (YGGFL, LDIFSDF, LDIFSDFR and RLDIFSDF) were produced using an electrospray source. These ions were used as thermometer probe compounds. Cone voltages (V(c)) were linearly correlated with the mean internal energy values (<E(int) >) carried by desolvated ions. These mean internal energy values seem to be slightly dependent on the size of the studied ion. ESI mass spectra and CID spectra were then simulated using the MassKinetics software to propose an empirical equation for the mean internal energy (<E(int) >) versus cone voltage (V(c)) for different source temperatures (T): < E(int) > = [405 x 10(-6) - 480 x 10(-9) (DOF)] V(c)T + E(therm)(T). In this equation, the E(therm)(T) parameter is the mean internal energy due to the source temperature at 0 V(c).

Monte Carlo calculation of Ising model with single‐site anisotropy energy in ferromagnetic iron nitride system

AbstractThe magnetic behavior of a mixed Ising ferromagnetic system on Fe4N expended face‐center cubic lattice, with single‐site anisotropy, has been studied with Monte Carlo Simulation. The expended face‐center cubic lattice was divided into one simple cubic lattice composed of Fe(I) at the corner site and three inhomogeneous simple cubic lattices composed of Fe(II) at the face‐centered one. The two sublattices have spin‐3/2 and spin‐1, respectively. The model includes nearest interactions and single‐site anisotropy terms. By studying magnetization, internal energy, specific heat of this model at different temperatures, we found that the absolute zero value of magnetization is changed by existence of Fe(I)'s and Fe(II)'s crystal‐field interactions (D1, D2). The final value of internal energy is different for different D1 and D2. Curie temperature is increasing with the increase of D1 and D2. Especially, equal point of sublattice magnetization was recognized, when D1 was changed. (© 2007 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Excess internal pressure, excess energy of vaporization and excess pseudo-Gruneisen parameter of binary, ternary and quaternary liquid mixtures

Densities, viscosities and ultrasonic velocities were measured for four binary, one ternary and one quaternary liquid systems at 298.15 K to obtain values of excess internal pressure and excess energy of vaporization. Values of pseudo-Gruneisen parameter and excess pseudo-Gruneisen parameter have been evaluated theoretically for two quaternary liquid systems. A quantitative relationship has been established among these thermodynamic properties with the help of relevant expressions. Study of molecular interaction has been made in the light of excess thermodynamic functions.

Surface Modification and Laser Pulse Length Effects on Internal Energy Transfer in DIOS

Benzyl-substituted benzylpyridinium (BP) chloride salts were used as a source of thermometer ions to probe the internal energy (IE) transfer in desorption/ionization on porous silicon (DIOS). To modify their wetting properties and the interaction energies with the thermometer ions, the DIOS surfaces were silylated to produce trimethylsilyl- (TMS), amine- (NH2), perfluoroalkyl- (PFA), and perfluorophenyl-derivatized (PFP) surfaces. Two laser sources--a nitrogen laser with pulse length of 4 ns and a mode locked 3 x omega Nd:YAG laser with a pulse length of 22 ps--were utilized to induce desorption/ionization and fragmentation at various laser fluence levels. The corresponding survival yields were determined as indicators of the IE transfer and the IE distributions were extracted. In most cases, with increasing the laser fluence in a broad range (approximately 20 mJ/cm2), no change in IE transfer was observed. For ns excitation, this was in remarkable contrast with MALDI, where increasing the laser fluence resulted in sharply (within approximately 5 mJ/cm2) declining survival yields. Derivatization of the porous silicon surface did not affect the survival yields significantly but had a discernible effect on the threshold fluence for ion production. The IE distributions determined for DIOS and MALDI from alpha-cyano-4-hydroxycinnamic acid reveal that the mean IE value is always lower for the latter. Using the ps laser, the IE distribution is always narrower for DIOS, whereas for ns laser excitation the width depends on surface modification. Most of the differences between MALDI and DIOS described here are compatible with the different dimensionality of the plume expansion and the differences in the activation energy of desorption due to surface modifications.

Evaporation dynamics of mixed Lennard-Jones atomic clusters

Molecular dynamics (MD) simulations have been run to study the evaporation process of a model Lennard-Jones cluster, namely ArnXm, in which X is an artificial atom whose properties can be adjusted. The influence of changes in its Lennard-Jones parameters (binding energies D and distance σ) and its mass has been explored in a systematic way in the case of various seven-atom clusters on: (i) The outcome of Ar3X4 evaporation (chemical composition of the product cluster) and (ii) the evaporation rate constant in the series of Ar7−mKrm. It is shown that a proper choice of the X atom parameters allows to enhance the evaporation rate constant of ArnX in a way which enables to explore by MD the dynamics at much lower values of internal energy. Consequently the “melting” transition in Ar7 and Ar13 product clusters can be investigated by the analysis of the mean kinetic-energy release. In the latter case it is shown to be in excellent agreement with phase space theory predictions.

Fisher and Jaynesian statistics compared in the description of classical fluids

Fisher statistics provides an information measure which, like that of Shannon, is a functional of a distribution f. The latter solves an Euler equation to minimize the functional. To make comparison with statistical derivations of extended thermodynamics, calculations by Frieden, Plastino, and collaborators are specialized to the case where f is a phase-space distribution approximating a solution of the Liouville equation. The Euler equations are solved subject to conditions specifying values of internal energy and fluxes, e.g. of heat and momentum. The solution is compared with that of Jaynes which, with information theory, provides an entropy model. The Fisher and Jaynes entropies are identical only in equilibrium. The distributions agree in linear approximation for a restricted set of variables. This set is large enough to embrace all those needed in the classical non-equilibrium description of simple fluids. Fisher-Euler solutions are not unique in non-equilibrium.

Thermodynamic analysis of compact formation; compaction, unloading, and ejection: II. Mechanical energy (work) and thermal energy (heat) determinations of compact unloading and ejection

A compaction calorimeter, previously described (DeCrosta, M.T., Schwartz, J.B., Wigent, J.B., Marshall, K., 2000. Thermodynamic analysis of compact formation; compaction, unloading, and ejection. I. Design and development of a compaction calorimeter and mechanical and thermal energy determinations of powder compaction. Int. J. Pharm. 198, 113–134), was utilized to evaluate the thermodynamics of the unloading and ejection of compacts of Avicel® pH102, Emcompress®, Fast-Flo #316®, Starch 1500, and acetaminophen (APAP). A constant strain waveform, applied by a compaction simulator, enabled the separate thermodynamic evaluation of unloading from compaction. The brittle materials, Fast-Flo #316® and Emcompress®, displayed the most unloading work, and the plastic/self-lubricating materials, Avicel® and Starch 1500, displayed the least. Unloading heat values were negative for all materials, except APAP. APAP's positive heat values indicated the breaking of bonds during unloading as a result of its highly elastic nature. Positive internal energy changes of unloading, which indicate the net breaking of bonds, were observed for APAP and Emcompress® over the compaction forces tested. Negative energy changes for Starch 1500, Fast-Flo #316®, and Avicel® became positive with increasing compaction forces. Ejection work increased with increasing compaction force for the brittle materials, whereas smaller ejection work values for Avicel®, Starch 1500, and APAP remained constant. Increasing negative heat values as a function of compaction force were observed for Fast-Flo #316® and Emcompress®. Negative internal energy values for ejection were observed for Fast-Flo #316® and Emcompress®, which indicates net bond formation as a result of high shear of the compact with the die wall. Internal energy changes for Starch 1500, Avicel®, and APAP, were approximately zero, indicating the absence of net bonding or bond formation during the process.

Superdense State of Metals Compressed by Shock Waves.

The paper presents explosive devices designs for generation of strong shock waves. Record values of specific internal energy of shock-compressed iron are obtained with use of them.

A note on the variation of Young's modulus, absorptive power of impactive energy, fracture toughness and creep strain rate during the creep process

Most of the early research on creep was confined to obtaining data for correlating the expected rupture time of a sample with the static creep stress, the variation of the mechanical properties not having been studied during the creep process. Young's modulus decreases as the Larson-Miller parameter increases. The static load multiplied by the tensile elastic deformation caused by the decrease of the value of Young's modulus supplies internal energy for creep deformation. Young's modulus decreases linearly with time during the creep test from polycrystalline value at the start of the test to a microstructural minimum value at the Larson-Miller parameter at the creep stress. This is caused by the rotation of the grain during the creep shear deformation. The absorptive power of impactive energy increases linearly with time but the fracture toughness decreases quickly.

Time-Resolved Photodissociation Rates and Kinetic Modeling for Unimolecular Dissociations of Iodotoluene Ions

Time-resolved photodissociation rate measurements are reported for the unimolecular dissociation of the three iodotoluene ion isomers at two values of internal energy (2.54 and 2.67 eV). For the para isomer, the rate constants are in agreement with previous experimental information. The meta isomer is roughly similar to para, but the ortho isomer dissociates roughly 5 times faster at the same internal energies. These new data, along with prior results, are fitted into a comprehensive two-channel model of the dissociation kinetics, assuming competitive dissociation to form tolyl ions, and either benzyl or tropylium ions. Activation energies and entropies are assigned to both dissociation channels for each isomer

Extension of the SWLE equation of state to property calculations for soft-core fluids

Abstract Shen, S. and Lu, B.C.-Y., 1993. Extension of the SWLE equation of state to property calculations for soft-core fluids. Fluid Phase Equilibria 86: 27-46 The previously developed four-parameter perturbed hard-sphere equation of state based on the square-well-linear-extension (SWLE) potential is extended to the property calculations for soft-core fluids. The predicted values of configurational Helmholtz free energy, configurational internal energy, compressibility factor and second virial coefficient for the Lennard-Jones fluid over a wide range of reduced density (ϱ ★ = 0.02–2.50) and reduced temperature ( T ★ = 0.591–100) are in good agreement with the computer simulation data. The predicted values of configurational internal energy (ϱ ★ =0.1–1.25, T ★ = 0.81169–811.69) and compressibility factor (ϱ ★ = 0.6–0.7, T ★ = 0.81169–811.69) for the modified Buckingham (6-exp) fluid are also satisfactory. For data correlation, the SWLE equation yields comparable accuracy with the 33-parameter equation of Adachi et al. (1988), [Adachi Y., Fijhara, T., Takamiya, M. and Nakanishi, K., 1988. Generalized equations of state for Lennard-Jones Fluids. I. Pure fluids and simple mixture. Fluid Phase Equilibria, 39: 1-38], based on the investigated thermodynamic properties of the Lennard-Jones fluid.

Molecular dynamics study of propane using two simple potential models

Two empirical potential models for propane are presented. The potential parameters were chosen to fit the experimental second virial coefficient and the bubble densities of propane. With the obtained parameters, the agreement between molecular dynamics simulation results for pressure, internal energy, and experimental values of these properties is good. We also present simulated results for the properties of a reference anisotropic system defined within the WCA spirit. Rapid convergence of the perturbation scheme is clearly shown; giving the computed values of A1 and A2. These values can be useful to test the different approximations contained in a perturbation theory recently proposed for these types of potentials. In addition, we also evaluate from the simulations, the estimated value of the self-diffusion coefficient of propane.