Simulations surface temperature elevation

Simulation of Surface Temperature Elevation of Polyimide Film... 

In some situations we have performed finite temperature molecular dynamics simulations [50, 51] using the aforementioned model systems. On a simplistic level, molecular dynamics can be viewed as the simulation of the finite temperature motion of a system at the atomic level. This contrasts with the conventional static quantum mechanical simulations which map out the potential energy surface at the zero temperature limit. Although static calculations are extremely important in quantifying the potential energy surface of a reaction, its application can be tedious. We have used ah initio molecular dynamics simulations at elevated temperatures (between 300 K and 800 K) to more efficiently explore the potential energy surface. 

Visual detection of surface layers on cathodes using microscopy techniques such as SFM seems to be supportive of the existence of LiF as a particulate-type deposition.The current sensing atomic force microscope (CSAFM) technique was used by McLarnon and co-workers to observe the thin-film spinel cathode surface, and a thin, electronically insulating surface layer was detected when the electrode was exposed to either DMC or the mixture FC/DMC. The experiments were carried out at an elevated temperature (70 °C) to simulate the poor storage performance of manganese spinel-based cathodes, and degradation of the cathode in the form of disproportionation and Mn + dissolution was ob-served. °° This confirms the previous report by Taras-con and co-workers that the Mn + dissolution is acid-induced and the electrolyte solute (LiPFe) is mainly responsible. 

Our ultimate goal is the simulation of alloys and their behavior under conditions of elevated temperature. Accordingly, empirical multibody potentials present an attractive combination of physical accuracy and computational efficiency. To facilitate simulation under the widest possible variety of conditions of temperature, pressure, and surface tension, we decided to incorporate a multibody potential function for copper into a widely used, commercially available molecular dynamics program. We chose CHARMM [35], because of its widespread use, constant pressure/ temperature/surface tension capabilities, and reliability. 

Quantum-chemical simulation in a cluster approach has shotvn that introduction of hydrogen in silicon nanoclusters leads to initial stages of silicon layers amorphization, whereas oxygen atoms play a role of the stabilizing factor forming initial stmctures of silicon oxide from amorphized silicon layers. The experiments have demonstrated that H, He and Ar ion-beam treatments have a qualitatively similar impact on the electrical properties of Si wafers and are caused by the formation of point defects by ions (independing of ion type) and the creation of donors in the under-surface wafer region (only in a caseof H -treatment at elevated temperatures). 

The results stated so far has been with saturated vapor or liquid as the equilibrium bulk phase. Liquid-like state in pore, however, can hold with reduced vapor pressure in bulk the well-known capillary condensed state. One of the most important feature of the capillary condensation is the liquid s pressure Young-Laplace effect of the curved surface of the capillary-condensed liquid will pull up the liquid and reduce its pressure, which can easily reach down to a negative value. In the section 2 we modeled the elevated freezing point as a result of increased pressure caused by the compression by the excess potential. An extension of this concept will lead to an expectation that the capillary-condensed liquid, or liquid under tensile condition, must be accompanied with depressed freezing temperature compared with that under saturated vapor. Then, even at a constant temperature, a reduction in equilibrium vapor pressure would cause phase transition. In the following another simulation study will show this behavior. 

Corrosion. Fink 16) of Battelle Memorial Institute has presented the results of a literature study combined with views of experts on the corrosion of metals by sea water. The study revealed a paucity of data on corrosion at elevated temperatures. The Cl ion is the chief culprit in causing corrosion, but an important factor is dissolved oxygen and it is probable that oxygen-free sea water would have very little corrosive action, at least at ordinary temperatures. Natural sea water may have very different corrosion effects from synthetic sea water because of the organic content. Fouling of the surface by organic deposits can lead to severe pitting due to concentration-cell effects. Consequently corrosion by actual water is not readily simulated in the laboratory by synthetic sea water. 

The approach we have discussed here addresses both problems with comparable emphasis. The density functional formalism, with the LSD approximation for the exchange-correlation energy, provides us with an approximate method of calculating energy surfaces, and the results have predictive value in many contexts. DF can also be carried out with comparable ease for all elements. When coupled with MD at elevated temperatures (simulated annealing), it is possible to study cases where the most stable isomers are unknown, or where the energy surfat have many local minima. 

It is apparent that, in addition to providing the potential energy surface description, the computational treatment must account for the physical situation to accurately describe the system at hand. The most accurate potential can yield information only as complete as the search or simulation algorithm that employs it will permit. In this case it is reassuring to note that the low energy diffusion pathways obtained in static simulation are confirmed in lengthy molecular dynamics calculations. It is also worth noting that the dynamics calculation shows that less commonly accessed diffusion pathways are of importance in the system at elevated temperatures. 

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