## Elastic constants of nickel: Variations with respect to
temperature and pressure

Cagin-T and Pettitt-BM

Physical Review B**39**, 12484-12491(1989)

## ABSTRACT

The temperature dependence and pressure derivatives of the adiabatic
second and third-order elastic coefficients of metallic nickel are
calculated from molecular dynamics. We employ a Morse potential
parametrized from lattice sums for nickel to model interactions
between the atoms. The elastic coefficients are obtained at three
different temperatures (T=300, 482 and 67 K) from statistical
fluctuation expressions. By use of the zero-pressure second and
third-order elastic coefficients, the pressure derivatives of second
order elastic coefficients of nickel on the aforementioned
isotherms are also obtained. The difference between theoretical
and experimental second-order elastic coefficients are found to vary from
4% to 14%. The largest differences are seen for higher temperatures.
The theoretical values for C11 and C12 are smaller than the
experimental values, whereas the results for C44 are larger than the
experimental values. The parametrized Morse potential used in
these calculations cannot quantitatively reproduce the thirdorder
elastic coefficients at T=300 K. For example, the differences between
the calculated results and the experimental values at T=300 K are
larger than 20% for some moduli. The comparably large magnitude of
the fluctuation terms appearing in the statistical formulas for the
elastic coefficients shows the importance of the thermal and anharmonic
effects which are not accounted for in the lattice sums and
harmonic lattice dynamics.