def calc_CoCoO(P, T):
	"""
	Cobalt-Cobalt Oxide (CoCoO)
	===========================
	Define CoCoO buffer value at P

	Parameters
	----------
	P: float
		Pressure in GPa

	T: float or numpy array
		Temperature in degrees K

	Returns
	-------
	float or numpy array
		log_fO2

	References
	----------
	B. R. Frost in Mineralogical Society of America "Reviews in Mineralogy" Volume 25
	"""
	# translate P to bars
	P_bars = P*10000

	log_fO2 = (-24332.6/T) + 7.295 + 0.052 * (P_bars-1)/T
	return log_fO2