![]() ![]() Molec_energy ≔ Energy molec, method = energymethod, basis = energybasis, spin = 2 ⋅ molec_spin, charge = molec_charge au2Jmol ≔ 4.359744650&ExponentialE −18 ⋅ evalf Constant Avogadro_constant : molec_energy ≔ molec_energy ⋅ au2Jmol # molec,molec_data&Assign GeometryOptimization molec, energymethod, basis = energybasis, spin = 2 ⋅ molec_spin, charge = molec_charge Ĭalculate electronic energy in J/mol using AOmethod, AObasis, spin, and charge defined above: If not using Hartree-Fock and sto-3g, uncomment the following line: Doesn't matter which is 1, 2, or 3, just keep track! Molec_index ≔ 2 : # identifies which reactant or product. Molec_spin ≔ 0 : # molec_spin = 0 for singlet, molec_spin = 1 for tripletįreqmethod ≔ ' HartreeFock ' :Įnergymethod ≔ ' HartreeFock ' :įreq_scaling ≔ 0.8953 : # see Ref. Molec_symmetry_number ≔ 2 : # symmetry number # molec&Assign ReadXYZ ethyleneoxide.xyz xyz coordinates for each molecule and uncomment the geometry optimization line below. If you wish to use a different method/basis combination, begin with the provided. xyz data files are at the HartreeFock / STO-3G level. Here we specify the coordinates of the molecule for which we want to calculate thermodynamics as well as some related calculate parameters, such as symmetry number, charge, AObasis, etc. Restart : with QuantumChemistry : with ScientificConstants : with LinearAlgebra : Digits ≔ 15 : We begin with initializing the QuantumChemistry package, along with the ScientificConstants and LinearAlgebra packages. ![]() We will calculate S, H, and G for each of the reactants and product in Rxn (1) and calculate ΔH, ΔG, and ΔS as Note we have corrected for the vibrational zero-point-energy for the internal energy. Once the translational, electronic, rotational, and vibrational thermal contributions to the total entropy and internal energy have been calculated, total entropy ( S ), internal energy ( E ), enthalpy ( H ), and free-energy ( G ) can be calculated as follows: Where s = 3 N - 5 normal modes for a linear molecule and s = 3 N - 6 for a nonlinear polyatomic. Where Θ A, &Theta B, &Theta C are the rotational temperatures corresponding to the principal moments of inertia. Each molecule we will consider in this activity is characterized by σ r = 2. Where &sigma r is the rotational symmetry number and &Theta r is the rotational temperature. The thermal contribution to internal energy is 0 since the q e does not depend on temperature. These assumptions lead to the following expressions for q, S, and E : To calculate q, we further assume each species is in the ground electronic state (with degeneracy 2 spin + 1) with rovibrational energies given by harmonic oscillator and rigid rotor approximations. Where q is the molecular partition function q e = q t q e q r q v, where the subscript t, e, r, and v refer to the translational, electronic, rotational, and vibrational contributions, respectively. The thermal entropy ( S ) (J/mol K) and the internal energy ( E ) (J/mol) are given by: To simplify the calculations, you will treat each species as an ideal gas. In this activity, you will apply statistical thermodynamics to calculate the enthalpy, free energy, and entropy of reaction for the combustion of ethene to form ethylene oxide at 298 K: Statistical Thermodynamics: Calculating Thermodynamic Functions DH, DG, and DSĬalculate ΔH, ΔG, and ΔS (after completing above for all reactants and products) ![]()
0 Comments
Leave a Reply. |