  The time evolution of wavepackets in crystals in the presence of a
homogeneous electric field is formulated in k-space in a numerically tractable
form. The dynamics is governed by separate equations for the motion of the
waveform in k-space and for the evolution of the underlying Bloch-like states.
A one-dimensional tight-binding model is studied numerically, and both Bloch
oscillations and Zener tunneling are observed. The long-lived Bloch
oscillations of the wavepacket center under weak fields are accompanied by
oscillations in its spatial spread. These are analyzed in terms of a k-space
expression for the spread having contributions from both the quantum metric and
the Berry connection of the Bloch states. We find that when sizeable spread
oscillations do occur, they are mostly due to the latter term.
