Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Thermodynamic model of hardness: Particular case of boron-rich solids   A number of successful theoretical models of hardness have been developed
recently. A thermodynamic model of hardness, which supposes the intrinsic
character of correlation between hardness and thermodynamic properties of
solids, allows one to predict hardness of known or even hypothetical solids
from the data on Gibbs energy of atomization of the elements, which implicitly
determine the energy density per chemical bonding. The only structural data
needed is the coordination number of the atoms in a lattice. Using this
approach, the hardness of known and hypothetical polymorphs of pure boron and a
number of boron-rich solids has been calculated. The thermodynamic
interpretation of the bonding energy allows one to predict the hardness as a
function of thermodynamic parameters. In particular, the excellent agreement
between experimental and calculated values has been observed not only for the
room- temperature values of the Vickers hardness of stoichiometric compounds,
but also for its temperature and concentration dependencies.

2
The categories of this paper are: math
0
The categories of this paper are: hep-ph
3
The categories of this paper are: physics
33
The categories of this paper are: plasm-ph
8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
19
The categories of this paper are: eess
13
The categories of this paper are: quant-ph
15
The categories of this paper are: nucl-ex
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
25
The categories of this paper are: patt-sol
27
The categories of this paper are: comp-gas
11
The categories of this paper are: hep-lat
7
The categories of this paper are: hep-th