def avgchrg(self, inpfname):
"""
Read charge from PW output file, compute the average z-charge
The most cost routine in the Class
"""
chrgdata = PlotIORead(inpfname, "ang")
slabchrg = ChrgAvgZ(chrgdata.ary3d, chrgdata.cell)
avgchrg = slabchrg.xyavg() # *slabchrg.xyarea()
return avgchrg
