Random potential energy

The early conductivity model of Stevels (1957) and Taylor (1956, 1959) is in a sense a random potential energy model. It is assumed in this model that the ions experience randomly varying potential energy which is due to the presence of a random structure. For the d.c. conduction, the... 

Experimentally one generally distinguishes several spin- lattice (longitudinal) relaxation times, Tipd, Tig, Tip etc.. In glasses due to the presence of random potential energy barriers, the relaxation times exhibit a distribution. In general, they can be expressed as ... 

Construction In tin dioxide semiconductor sensors, the sensing material is small sintered particles. For the sensor current flow, particle boundaries form potential energy barriers, which act as a random barrier netw ork. Different types t)f semiconductor gas sensors are shown in Fig. 13..54. 

We do this as follows. The N particles are placed in a starting configuration, for example a regular lattice. Each particle is then tentatively moved at random. For each move, we calculate the change in the mutual potential energy, AU. If At/ is negative, then we allow the move. If At/ is positive, we allow the move with a probability of expi—U/kaT). 

Experiment shows that heat is absorbed as iodine dissolves. The regular, ideally packed iodine crystal gives an iodine molecule a lower potential energy than does the random and loosely packed solvent environment. We see that the second factor, tendency toward minimum energy, favors precipitation and growth of the crystal. 

In cubic close-packing each molecule is surrounded by twelve others, whose interaction with the central molecule can be represented by a potential function of cubic point-group symmetry in case that the twelve molecules are spherically symmetrical or oriented at random. The energy change produced by this potential function,/say, is... 

The motion of particles of the film and substrate were calculated by standard molecular dynamics techniques. In the simulations discussed here, our purpose is to calculate equilibrium or metastable configurations of the system at zero Kelvin. For this purpose, we have applied random and dissipative forces to the particles. Finite random forces provide the thermal motion which allows the system to explore different configurations, and the dissipation serves to stabilize the system at a fixed temperature. The potential energy minima are populated by reducing the random forces to zero, thus permitting the dissipation to absorb the kinetic energy. 

The local conformational preferences of a PE chain are described by more complicated torsion potential energy functions than those in a random walk. The simulation must not only establish the coordinates on the 2nnd lattice of every second carbon atom in the initial configurations of the PE chains, but must also describe the intramolecular short range interactions of these carbon atoms, as well as the contributions to the short-range interactions from that... 

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