  New interatomic potentials describing defects, plasticity and high
temperature phase transitions for Ti are presented. Fitting the martensitic
hcp-bcc phase transformation temperature requires an efficient and accurate
method to determine it. We apply a molecular dynamics (MD) method based on
determination of the melting temperature of competing solid phases, and
Gibbs-Helmholtz integration, and a lattice-switch Monte Carlo method (LSMC):
these agree on the hcp-bcc transformation temperatures to within 2 K. We were
able to develop embedded atom potentials which give a good fit to either low or
high temperature data, but not both. The first developed potential (Ti1)
reproduces the hcp-bcc transformation and melting temperatures and is suitable
for the simulation of phase transitions and bcc Ti. Two other potentials (Ti2
and Ti3) correctly describe defect properties, and can be used to simulate
plasticity or radiation damage in hcp Ti. The fact that a single EAM potential
cannot describe both low and high temperature phases may be attributed to
neglect of electronic degrees of freedom, notably bcc has a much higher
electronic entropy. A temperature-dependent potential obtained from the
combination of potentials Ti1 and Ti2 may be used to simulate Ti properties at
any temperature.
