What accuracy do we need? Usually errors in computed or estimated energies dominate, because they appear in the exponents in the expressions for k∞(T) and Keq(T). Since Keq=exp(-∆Grxn/RT), if the computed value of the energy contains an error δG ∆Grxn,computed = ∆Grxn,true + δG Keq,computed = Keq,true exp(δG/RT) So if |δG|>RT, that error will cause Keq,computed will be off by a factor of e ≈ 2.7x or more from the true value. Similarly, if the computed reaction barrier differs from the true barrier height by δE, kcomputed = ktrue exp(δE/RT) So if |δE| > RT, that error in the computed barrier energy will cause the computed rate coefficient k to be off by a factor of 2.7x or more.