Introduction To Quantum Chemistry Lecture Notes PDF

INTRODUCTION TO QUANTUM CHEMISTRY AP TS DR WAN NOR ROSLAM WAN ISAHAK DEPARTMENT OF CHEMICAL AND PROCESS ENGINEERING UNIVERSITI KEBANGSAAN MALAYSIA Without Quantum Mechanics, how would you explain: Periodic trends in properties of the elements e.g. Tetr...

INTRODUCTION TO QUANTUM CHEMISTRY AP TS DR WAN NOR ROSLAM WAN ISAHAK DEPARTMENT OF CHEMICAL AND PROCESS ENGINEERING UNIVERSITI KEBANGSAAN MALAYSIA Without Quantum Mechanics, how would you explain: Periodic trends in properties of the elements e.g. Tetrahedral carbon in ethane, planar Structure of compounds ethylene, etc. Bond lengths/strengths Discrete spectral lines (IR, NMR, Atomic Absorption, etc.) Electron Microscopy & surface science Without Quantum Mechanics, chemistry would be a purely empirical science.  Computing ideal gas thermodynamic and Quantum spectroscopic properties Chemical Predict the structures of molecules Calculation s in Analyzing reaction pathways Chemical Process Calculation of heats of formation and related Industry properties Interaction energies + molecular simulation to predict thermodynamic properties of nonideal systems  Computing the Thermodynamic and Spectroscopic properties Thermodynamic properties - Ideal gas lawa (PV= nRT - Internal energy (U= nCvT) - Enthalpy (H= U + PV = nCvT - Work done & heat transfer - Thermodynamic processes: Isothermal, Adiabatic, Isobaric Spectroscopic properties - Energy level: a) Rotational energy levels b) Vibrational energy levels - Spectra: Spectrum, electronic transitions - Absorption and Emission  Computing the Thermodynamic and Spectroscopic properties Computational Methods/ Quantum chemistry: Gaussin, VASP, etc to compute molecular properties, energy levels and spectra using quantum methods. Molecular simulation: Molecular dynamics or Monte Carlo simulations (Thermodynamic properties of gases under varios conditions)  Molecular Structure Prediction Based on potential energy surfaces (PES)  represent energy of a system: - Molecular mechanics: bond lengths, bond angles, torsion angles, van der Waals interactions, and electrostatics. - Quantum mechanics: More accurate. Methids: Hartree- Fock (HF) and Density Functional Theory (DFT) - Geometry optimization: Minimize energy of a molecular system (most stable)  Analyzing Reaction Pathways Reaction coordinate: potential energy surface as a reaction coordinate, where the highest energy point is the transition state. Transition state search Calculated using Quantum chemical method: DFT or HF The Electromagnetic Spectrum  As the frequency of light increases, the energy increases. As the wavelength of light increases, the energy decreases. Red light (650 nm) This doesn’t seem like much, but when you consider a mole of photons is; 184 kJ/mol  Determine the wavelength (in nm) associated with an electron jumping from n= 2 to n=5 in a hydrogen atom. The value of ∆E is positive because this is an absorption.  Determine the wavelength (in nm) associated with an electron jumping from n= 2 to n=5 in a hydrogen atom.  In 1905, Albert Einstein used Planck’s Law to explain the photoelectric effect. The Wave-like Nature of a Paticle Louis de Broglie in response to Planck & Einstein’s assertion that light was “particle-like” (photon) stated that small particles moving fast could exhibit a characteristic wavelength. Conclusion: Light waves have mass, particles have a wavelength. Compton Effect  END.. THANK YOU..