Can I take H = 0 at absolute zero

I am a 12th grade students making a reaction engine(includes state change, solvation also) on java, I was wondering can I take enthalpy(heat not change in heat) of a substance 0 at P(ext.) = 1, Kinetic energy = 0 and temperature = 0k(-273.15°C). from there I can take H approximately at temp. = t(at any temperature from there on). Note: I want to calculate H not ΔH. Or You may have any suggestions then please tell me.




First of all, I deeply appreciate your work. At absolute zero, only the entropy of a perfect crystal is zero. It is the third law of thermodynamics. A system has energy, even if the temperature is $0$ K.


Consider for example a monodimensional quantum oscillator. Solving the associated Schrödinger equation, you obtain the energy
$$
E =\biggl(n + \frac{1}{2}\biggr)h\nu
$$
where $n$ is the vibrational quantum number, $h$ is the Planck constant, and $\nu$ is the frequency associated with the oscillator.


At $0$ K, you are in the lowest possible state. Therefore $n=0$, but the energy is not zero
$$
E=\frac{1}{2}h\nu
$$


This energy is known as *Zero Point Energy*, then the energy is not zero, otherwise, it will violate the Heisenberg principle.


I want to remark on the physical chemistry of the problem. You can do this approximation, saying that the heat at $0$ Kelvin is zero. You consider this heat as a constant and impose it to zero.


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