Thermodynamic properties and phase transitions in CO2 molecular clusters

Abstract

The thermodynamic properties of (CO2) N molecular aggregates of size 2 ⩽ N ⩽ 13 have been investigated. These crystallites exhibit well defined orientational order–disorder rotational transitions accompanied by a structural transition into a plastic crystallite phase. In addition, they exhibit melting and disassociation transitions. It is shown that the interpretation of experimental data, based upon dimer properties, depends crucially on these results. Equilibrium structures and orientations are also given.

Raman spectroscopy of supersonic jets of CO2: Density, condensation, and translational, rotational, and vibrational temperatures

“…However, no quantitative comparison is possible due to the qualitative nature of the Rayleigh scattering data reported. 17 Monte Carlo simulation of the thermodynamic properties of (CO 2 ) n clusters of size up to nϭ13 show that, in general, such clusters are not stable at temperatures above 80 K. 66 This agrees too with the trends shown in Figs. 5͑a͒ and 5͑b͒, where the sudden change of slope of T r near this temperature may be related to the fast growth of the energy released by condensation.…”

Resonance and Threshold Phenomena in Low-Energy Electron Collisions with Molecules and Clusters

“…According to molecular dynamics simulations (Etters et al, 1981;Tsukada et al, 1987;Torchet et al, 1996;Maillet et al, 1998), neutral carbon dioxide clusters possess icosahedral structure (at least for sizes up to about N ¼ 20) with predicted binding energies around 0.14 eV per molecule for N ¼ 13 (Maillet et al, 1998); at sizes above about N ¼ 30, a transition to bulk cubic structure has been predicted, and this bulk structure has been experimentally verified for N above about 100 (Torchet et al, 1996). Some information on cluster anion structures is also available.…”

Effect of Formation of van der Waals Complexes on Molecular Physical Properties

“…From Eqs. (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) and (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19) we can see that the measurement of the spectral shift or ionization potential as a function of cluster size n in MAn can be used as a probe to study the molecular dynamics of clusters. [2][3][4][5][6][7] Investigations concerning the formation and properties of small clusters comprise an active area of research both experimentally and theoretically.…”

“…Notice that for example (3)(4)(5)(6)(7)(8)(9) where ei(M) denotes the orbital energy for the i-th MO belonging to M. Next we consider the case of large n values; in this case except for a small number of adsorbed A's in the first several layers of MAn, the remaining adsorbed A's in MAn can be described by a distribution function gia(r). That is, E(n)i--,a--AEd(n)i--,a q-AE(n) (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17) where Ea(n)i-,a n[AE(a) Ai Here for simplicity it is assumed that besides n, na,.., the adsorbed A's are continuously distributed between ro and R. Notice that p in Eq. From Eqs.…”

“…on the ionization potential due to the vdW complex formation can be treated similarly by using Eq. (3)(4)(5)(6)(7)(8) so its treatment will not be given here. It should be noted that, in this case, as n in MA approaches the macroscopic value, the mechanism of photoionization may not be the same as that for small n.…”