Radiation Chemistry. V. Effect of Molecular Size

A Monte Carlo study of the structure and thermodynamic behaviour of small Lennard-Jones clusters

“…The total number of interatomic distances per particle in the vicinity of r 0 is however equal to 3.22 and the second peak of n(r) appears at about r0~/3 but not at r0~/2 as with the f.c.c, packing. Such a structure coincides exaCtly with the NCI structure derived in [8,9] through potential energy minimization. Note that in all calculations with 13 atoms we took the f.c.c, structure as the starting point of the MC run.…”

“…This fact can be readily verified by integrating the expression dF=-PdV from zero density to d. It is of interest that the NCI structure possessed a lower internal energy (by ~5 per cent) than the f.c.c, structure, so that the relative stability of the f.c.c, cluster in this region could be attributed to entropy reasons. This result provides a striking example of the situation when the potential energy calculations such as performed in [8,9,17] may lead to erroneous conclusions about the cluster structure at non-zero temperatures. At densities below 1.16 a region was observed that can be probably interpreted as a two-phase region.…”

“…composed of particles interacting via a Lennard-Jones potential of the form ~(r) =,[(rolr)'*-2(rolr)q, (1) where ~ is the well depth and r 0 the position of minimum of the potential curve. Earlier papers on these microclusters were concerned with calculating the minimum energy structures, that is, the structures stable at absolute zero temperature [8,9]. The number of atoms in the clusters was usually taken "~ To whom correspondence should be addressed.…”

Particle size and interfacial effect on the specific heat of nanocrystalline Fe

“…No T 2 term appears in the total temperature range for the bulk Fe. Comparing with the specific heats of nano-Fe and bulk Fe, two additional terms, T 2 associated with surface modes of lattice vibrations [8][9][10][11] and (1/T 2 )e (AϪB/T) appear in C pn expression. Besides, the electronic specific coefficient ͑Sommerfeld co-efficient͒ ␥ of the nano-Fe sample decreases by about 50% comparing with that of the bulk iron.…”

The Structure of Liquid Methanol

“…[33,34] QCE is based on an earlier idea, namely, the construction of a global partition function from a superposition of local minimum structures. [35][36][37][38][39][40][41] Compared to earlier attempts, the QCE methodology differs in the additional cluster decomposition, the use of ab initio data for the clusters, and the quantum form of the vibrational partition function. Based on calculated ab initio properties of the constituent clusters (optimized structures, vibrational frequencies, binding energies), QCE theory employs the rigorous machinery of quantum statistical thermodynamics to calculate the partition functions and equilibrium cluster populations in the canonical ensemble.…”