  An increasing number of so-called superluminous supernovae (SLSNe) are
discovered. It is believed that at least some of them with slowly fading light
curves originate in stellar explosions induced by the pair instability
mechanism. Recent stellar evolution models naturally predict pair instability
supernovae (PISNe) from very massive stars at wide range of metallicities (up
to Z=0.006, Yusof et al. 2013). In the scope of this study we analyse whether
PISN models can match the observational properties of SLSNe with various light
curve shapes. Specifically, we explore the influence of different degrees of
macroscopic chemical mixing in PISN explosive products on the resulting
observational properties. We artificially apply mixing to the 250 Msun PISN
evolutionary model from Kozyreva et al. (2014) and explore its supernova
evolution with the one-dimensional radiation hydrodynamics code STELLA. The
greatest success in matching SLSN observations is achieved in the case of an
extreme macroscopic mixing, where all radioactive material is ejected into the
hydrogen-helium outer layer. Such an extreme macroscopic redistribution of
chemicals produces events with faster light curves with high photospheric
temperatures and high photospheric velocities. These properties fit a wider
range of SLSNe than non-mixed PISN model. Our mixed models match the light
curves, colour temperature and photospheric velocity evolution of two
well-observed SLSNe PTF12dam and LSQ12dlf. However, these models' extreme
chemical redistribution may be hard to realise in massive PISNe. Therefore,
alternative models such as the magnetar mechanism or wind-interaction may still
to be favourable to interpret rapidly rising SLSNe.
