  We use the quark potential model to calculate the mass spectrum of the S-wave
fully heavy tetraquark systems with different flavors, including the $ bc\bar
b\bar c, bb\bar c\bar c, cc\bar c\bar b $ and $ bb\bar b\bar c $ systems. We
employ the Gaussian expansion method to solve the four-body Schr\"odinger
equation, and the complex scaling method to identify resonant states. The $
bc\bar b\bar c, bb\bar c\bar c, cc\bar c\bar b $ and $ bb\bar b\bar c $
resonant states are obtained in the mass regions of $ (13.2,13.5) $, $
(13.3,13.6) $, $ (10.0,10.3) $, $ (16.5,16.7) $ GeV, respectively. Among these
states, the $ bc\bar b\bar c $ tetraquark states are the most promising ones to
be discovered in the near future. We recommend the experimental exploration of
the $ 1^{++} $ and $ 2^{++} $ $ bc\bar b\bar c $ states with masses near $ 13.3
$ GeV in the $ J/\psi\Upsilon $ channel. From the root-mean-square radii, we
find that all the resonant states we have identified are compact tetraquark
states.
