Argon lattice energy

Generally, increasing molecular size, heavier atoms and more polar bonds contribute to an increased lattice energy of a molecular crystal. Typical values are argon 7.7 kJ mol-1 krypton 11.1 kJmol-1 organic compounds 50 to 150 kJ mol-1. 

For the solid it is assumed that the total potential energy (i.e., lattice energy) is the sum of all pair potentials Ujj(rjj). The result of this summation for a face-centered cubic lattice (such as argon) is ... 

Finally, use Eq. (8) to determine the experimental value of the lattice energy of argon at 0 K. X-ray diffraction data give 5.30 A for the cubic unit-cell parameter of solid argon at 4 K. Find the nearest-neighbor distance d, and use Eqs. (10) and (11) to calculate a theoreticaf value of o- Compare the theoretical and experimental values. 

Three-body effects can significantly affect the dispersion interaction. For example, it is believed that three-body interactions account for approximately 10% of the lattice energy of crystalline argon. For very precise work, interactions involving more than three atoms may have to be taken into account, but they are usually small enough to be ignored. A potential that includes both two- and three-body interactions would be written in the following... 

The dipotassium salt is stable in solution or as a crystalline solid but it explodes on the least contact with oxygen or moisture and turns brown even in an atmosphere of nitrogen or argon [28,30]. The salts are thermodynamically very stable this is attributed partly to the ten ir-electron system but more especially to the large negative crystal lattice energy [33]. 

In the second test we optimised also on the lattice energy of Argon, which Is -7 7 0 kJ mol"" (-1.850 kcal mol ). It was given a weight 0.3 times the weight of lattice constants. The optimum was reached after 7 Iterations the results are given In Table 11-3 ... 

Calculations of the interaction energy in very fine pores are based on one or other of the standard expressions for the pair-wise interaction between atoms, already dealt with in Chapter 1. Anderson and Horlock, for example, used the Kirkwood-Miiller formulation in their calculations for argon adsorbed in slit-shaped pores of active magnesium oxide. They found that maximum enhancement of potential occurred in a pore of width 4-4 A, where its numerical value was 3-2kcalmol , as compared with 1-12, 1-0 and 1-07 kcal mol for positions over a cation, an anion and the centre of a lattice ceil, respectively, on a freely exposed (100) surface of magnesium oxide. 

Extensive computer simulations have been caiTied out on the near-surface and surface behaviour of materials having a simple cubic lattice structure. The interaction potential between pairs of atoms which has frequently been used for inert gas solids, such as solid argon, takes die Lennard-Jones form where d is the inter-nuclear distance, is the potential interaction energy at the minimum conesponding to the point of... 

Abstract. Gas interstitial fullerenes was produced by precipitation of C6o from the solution in 1,2 dichlorobenzene saturated by O2, N2, or Ar. The structure and chemical composition of the fullerenes was characterized by X-ray powder diffraction analysis, FTIR spectroscopy, thermal desorption mass spectrometry, differential scanning calorimetric and chemical analysis. The images of fullerene microcrystals were analyzed by SEM equipped with energy dispersive X-ray spectroscopy (EDS) attachment. Thermal desorption mass spectroscopy and EDS analysis confirmed the presence of Ar, N and O in C60 specimens. From the diffraction data it has been shown that fullerite with face centered cubic lattice was formed as a result of precipitation. The lattice parameter a was found to enhance for precipitated fullerene microcrystals (a = 14.19 -14.25 A) in comparison with that for pure C60 (a = 14.15 A) due to the occupation of octahedral interstices by nitrogen, oxygen or argon molecules. The phase transition temperature and enthalpy of transition for the precipitated fullerene microcrystals decreased in comparison with pure Cgo- Low temperature wet procedure described in the paper opens a new possibility to incorporate chemically active molecules like oxygen to the fullerene microcrystals. 

Figure 2. The minimum potential energy, tm, of a helium atom interacting with the 100 face of an argon crystal is plotted as a function of the position of the helium atom relative to the surface lattice...

The values used for e n, lattice parameters for argon and xenon at 0° K. The values of the parameters used in the calculation are listed in Table I. The potential functions which were obtained when these parameters were substituted in Equation 4.1 are shown in Figures 2 and 3. The potential energy at z — zm is plotted as a function of x (or y), the displacement of an adsorbed atom from the site center parallel to a site edge. It was found that the best simple representation of eT in the neighborhood of a site center on a face-centered cubic crystal is... 

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