pressure is converged when the relative error in pressure.PresTotlCurr - pressure.PresTotlCorrect
is less than conv.PressureErrorAllowed, which is reset with set pressure error command.

PressureChange
sets conv.lgConvPres true when pressure is converged

lgConvPres() returns true when pressure is converged (located in pressurechange.c)
sets pressure.PresTotlCorrect

header is pressure.h

current total pressure is pressure.PresTotlCurr
correct total pressure is pressure.PresTotlCorrect ;

ConvPresTempEdenIoniz
	called by cloudy, 
	calls PressureChange to evaluate current pressure and then change pressure
	to move toward correct value