THERMODYNAMICS OF THE MONOHYDROGEN DIFLUORIDES. II. HEAT CAPACITIES OF LITHIUM AND SODIUM MONOHYDROGEN DIFLUORIDES FROM 6 TO 305°K.¹

Structural characterization of sodium azide and sodium bifluoride at high pressures

“…However, unlike NaN 3 it does not undergo any temperature-induced phase transitions at atmospheric pressure and therefore no structural analogue of α-NaN 3 exists for NaHF 2 [48,49]. Furthermore, the high-pressure behaviour of sodium bifluoride has been shown to display very little in common with that of sodium azide.…”

Preliminary report on the thermodynamic properties of selected light-element and some related compounds:

“…The question of a double minimum in the bifluoride ion, analogous to the double minimum in the potential between oxygen atoms in a hydrogen bonded substance has been repeatedly examined by Westrum and his co-workers [32][33][34][35][36][37] and by others .…”

“…In particular, little evidence referring specifically to LiHFp has been presented except the crystal structure [56], which gives the F-F bond distance, and a heat capacity and vapor pressure study by Westrum and Burney [35]. Unfortunately, the calorimetric and vapor pressure measurements by Westrum and Burney, which could give decisive information on this point, are not complete.…”

“…This is not decisive, because the discrepancy can be attributed to another source, an error in the heat of formation selected by Cox and Harrop [29] for Z\H"[HF ( (a) and for the heat capacity of LiF(c). But the low temperature heat capacity measurements of LlHF 2 (c) [35] stop short of the range in which pressure measurements were made. Only an isolated A;apor pressure point in the range of the heat capacity measurements exists, and this was ued by Cox and Harrop [29] in their calculation.…”

“…Using the collective description of electron interactions developed by Bohm and Pines [32][33][34] , Pines determined a correlation energy of Ecorr = 0*0313 In(rg) -0*114 -0*005rg* ( 8 ) Later Nozieres and Pines [35] used this method to develop an interpolation procedure that gives for metallic densities the equation Ecorr= 0*031 In(rg) -0*115* ( 9 ) Carr, Coldwell-Horsf all and Fein [36] calculated the first anharmonic contribution to the ground state energy of an electron gas* They found for low densities or large r^the approximation …”