Thermodynamic Properties of the Group IA Elements

Abstract

This review describes thermodynamic properties of condensed phases of the alkali metals, excluding francium for which the amount of information is too limited. The properties considered are: heat capacities from 0 to 1600 K, temperatures and enthalpies of fusion and martensitic transformation in Li and Na; discussion on the Debye temperature and electronic heat capacity coefficient at absolute zero temperature is also included. The paper is the second part of a series. Similar to our previous assessment of the II A group, this paper considers original studies, especially with respect to factors which influence the accuracy and reliability of results. Recommendations derived from such analyses are compared with most advanced previous reviews made at the Institute for High Temperatures (Moscow) and the National Institute of Standards and Technology (Washington). The properties of individual elements of the group are compared and suggestions are made for experimental studies which should improve poorly measured quantities. The review is supplemented by an IBM PC database which contains references, assessed data, brief description of studies, and has facilities for fitting and plotting of data and for adding new information. §

Fragmentation phase transition in atomic clusters II

“…The experimental bulk specific heat is taken from refs. [20,21]. For antimony, as far as we know, there are no data available for the very low temperatures below T = 298 K. Here anharmonicities become unimportant and the specific heat can be computed within the Debye model, i.e.…”

“…[5,34]. The work function for ionisation of the bulk W ∞ [34,35], the ionization energy of the atom IP [34], the radius of the freeze-out configuration r f , the principal moments of inertia for the dimer I 2 [36,37] and for the trimer I 3 [38,39,40,33], the Debye temperature θ D [41,20], the melting and boiling temperatures T m and T v [20,34], the dimer and trimer frequencies ω d [37] and ω t [42],the maximum specific internal energy of the bulk ε max , and the bulk fissility coefficient χ. For simplicity we used in all cases for ε max the boiling energy at normal pressure.…”

Simulation of crystal and liquid potassium via restricted path-integral molecular dynamics

“…We simulate crystalline and liquid potassium metal with the method of PIMD. We have chosen potassium because ͑1͒ it is a prototype free-electron metal which has been studied previously by semiempirical pair potentials, ͑2͒ there exist experimental data for the pair-correlation function of the liquid state, 3 thermodynamic, 4 and vibrational properties. 5 The simulation cell contains 54 K ϩ and 54 nonpolarized electrons.…”

“…The choice of this system is essentially driven by its simplicity but also by the availability of experimental data such as structural and thermodynamic properties in both liquid and solid phases as well as vibrational properties for the crystal. [3][4][5] Although the alkali metals are often considered simple nearly free-electron systems ͑with only one single valence electron per atom͒, they possess physical properties that make them good prototype systems with relevance to many current issues in materials science. Some of these properties include ͑1͒ metal to nonmetal transitions ͑M/NM͒, the M/NM transition in expended molten alkali metals 6,7 remains an outstanding many-body problem of strongly correlated systems at high temperature; ͑2͒ immiscibility, while most binary alloys of alkali metals show miscibility, the K-Li and Na-Li exhibit a miscibility gap; 8 ͑3͒ structural phase transformations, the body-centered-cubic Na and Li crystals exhibit a martensitic transition at low temperature 4 but one of the most obvious and common transformations is that from the solid phase to liquid phase, namely, melting.…”

Charge Transfer and Dissociation in Collisions of Metal Clusters with Atoms

“…To obtain the total internal energy of the cluster, one has to add its initial thermal energy. For a given temperature, the latter has been obtained from the experimental curve relating temperature and internal energy of bulk Li [18]. The total internal energy is then used to evaluate the evaporation rate constants in the framework of the microscopic and microcanonical statistical theory of Weisskopf [19].…”