Thermodynamic state dependence of orientational order and rotational relaxation in carbon tetrachloride

Abstract

Molecular dynamics simulations show that orientational correlations in carbon tetrachloride span a wide range of distances within the phases that are ordinarily described as orientationally disordered. They are long ranged in the plastic crystal phase, reach up to several solvation layers in the liquid phase, and only involve contact neighbors within the gas phase. On the contrary, short range arrangements are rather similar, with the sequence face-to-face, edge-to-face, and edge-to-edge describing the most populated relative orientations for increasing distances. In what concerns rotational relaxation, it is shown that none of the available theories is able to describe the relationship between rotational relaxation and angular velocity relaxation times for the three phases studied. This is at variance with experimental results obtained long ago for carbon tetrafluoride, which were in excellent accord with J-diffusion, but is in line with recent experimental results for deuterated methane in gas-phase mixtures.

Comparison of the atomic level structure of the plastic crystalline and liquid phases of CBr2Cl2: neutron diffraction and reverse Monte Carlo modelling

“…For the determination of molecular orientations between tetrahedral molecules we prefer the following classification, due to Rey [2]: given a pair of tetrahedral molecules we construct two parallel planes, each one containing the centres of these molecules. Every molecular pair was labelled into one of six orientational classes, depending on how many halogens from each molecule are found between these planes.…”

“…During the last decade the structures of disordered (liquid) or partially disordered (plastic crystalline) phases of the series of CCl 4 [1][2][3][4], CBrCl 3 [5][6][7][8], CBr 2 Cl 2 [9][10], CBr 4 [11][12][13][14] halomethane compounds have been the object of many studies. One of the reasons for such an interest is that their molecular sizes are almost the same, with a nearly spherical molecular shape, whereas the molecular symmetry (and thus the dipole moment) covers a diverse range: T d (CCl 4 , CBr 4 ), C 3v (CBrCl 3 ) C 2v (CBr 2 Cl 2 ).…”

“…In this special phase the molecular centres are located in a highsymmetry lattice (face centered cubic, body centered cubic or rhombohedral), but the molecules can rotate around their equilibrium position. The three characteristic phases (ordered, plastic crystalline and liquid) have been studied extensively for each halomethane mentioned above [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16].…”

Is there a common orientational order for the liquid phase of tetrahedral molecules?

“…͑4͒ CCl 4 : The force field is that in Ref. 4. It was developed similarly to the one for neopentane; a comparison with the experimental total scattering function for both liquids can be found in Ref.…”

The plastic and liquid phases of CCl3Br studied by molecular dynamics simulations

“…Tetrahalomethanes with T d molecular symmetry have been the subject of many experimental and computational studies [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] . Compounds with lower symmetry (C 3v or C 2v ) have attracted so far some attention from the experimental groups 12,[18][19][20] , but very little work has been done from a computational point of view.…”