A Walkthrough For Quantum Chemistry Newbies Part 1: Basis Sets, Related Functions, and Usage by Peker Milas.

Slides:

Advertisements

Similar presentations

Basis Sets for Molecular Orbital Calculations

Advertisements

Electron Correlation Hartree-Fock results do not agree with experiment

Quantum Mechanics Calculations II Apr 2010 Postgrad course on Comp Chem Noel M. O’Boyle.

What Tools Can We Use? Ab Initio (Molecular Orbital) Methods – from the beginning full quantum method only experimental fundamental constants very high.

Statistical Mechanics and Multi- Scale Simulation Methods ChBE Prof. C. Heath Turner Lecture 03 Some materials adapted from Prof. Keith E. Gubbins:

CHE Inorganic, Physical & Solid State Chemistry Advanced Quantum Chemistry: lecture 4 Rob Jackson LJ1.16,

Solvation Models. Many reactions take place in solution Short-range effects Typically concentrated in the first solvation sphere Examples: H-bonds,

Molecular Quantum Mechanics

Introduction to Molecular Orbitals

Chapter 3 Electronic Structures

Chemistry 6440 / 7440 Semi-Empirical Molecular Orbital Methods.

Quantum Mechanics and Force Fields Hartree-Fock revisited Semi-Empirical Methods Basis sets Post Hartree-Fock Methods Atomic Charges and Multipoles QM.

Computational Chemistry

Introduction to ab initio methods I Kirill Gokhberg.

Basic Quantum Chemistry: how to represent molecular electronic states

Correlated ab Initio Methods. Goal: select the most accurate calculation that is computationally feasible for a given molecular system Model chemistry:

Case Studies Class 5. Computational Chemistry Structure of molecules and their reactivities Two major areas –molecular mechanics –electronic structure.

Quantum Mechanics Calculations

Minimal basis sets A common naming convention for minimal basis sets is STO-XG, where X is an integer. This X value represents the.

Chemistry 6440 / 7440 Electron Correlation Effects.

Basis Set. Basis Set ∞ Model chemistry: theoretical method and basis set … HF MP2 CCSD CCSD(T) CCSDT … Full CI Minimal Split-valence Polarized Diffuse.

Simulation of X-ray Absorption Near Edge Spectroscopy (XANES) of Molecules Luke Campbell Shaul Mukamel Daniel Healion Rajan Pandey.

Introduction to Computational Quantum Chemistry Ben Shepler Chem. 334 Spring 2006.

Ab Initio Molecular Orbital Theory. Ab Initio Theory n Means “from first principles;” this implies that no (few) assumptions are made, and that the method.

Molecular Modeling: Density Functional Theory C372 Introduction to Cheminformatics II Kelsey Forsythe.

Quantum Calculations B. Barbiellini Thematics seminar April 21,2005.

Computational Chemistry

Daniel Sánchez Portal Ricardo Díez Muiño Centro de Física de Materiales Centro Mixto CSIC-UPV/EHU centro de física de materiales CFM.

Practical quantum Monte Carlo calculations: QWalk

Molecular Modeling : Beyond Empirical Equations Quantum Mechanics Realm C372 Introduction to Cheminformatics II Kelsey Forsythe.

Lecture 6. Many-Electron Atoms. Pt.4. Physical significance of Hartree-Fock solutions: Electron correlation, Aufbau principle, Koopmans’ theorem & Periodic.

ChE 551 Lecture 23 Quantum Methods For Activation Barriers 1.

Model Chemistries Lecture CompChem 4 Chemistry 347 Hope College.

Basis Sets and Pseudopotentials. Slater-Type Orbitals (STO’s) N is a normalization constant a, b, and c determine the angular momentum, i.e. L=a+b+c ζ.

Lecture 11. Quantum Mechanics

Calculating Molecular Binding Energies from Chemical Bonds to van der Waals Interactions Thom H. Dunning, Jr. Joint Institute for Computational Sciences.

Some Problems (Precautions) of ab initio Quantum Chemistry Jim Jr-Min Lin Most papers only show the “good” sides of the calculation and hide the problematic.

Lecture 12. Basis Set Molecular Quantum Mechanics, Atkins & Friedman (4th ed. 2005), Ch Essentials of Computational Chemistry. Theories and Models,

1 MODELING MATTER AT NANOSCALES 6. The theory of molecular orbitals for the description of nanosystems (part II) Variational methods for dealing.

Optimization of Numerical Atomic Orbitals

Ab initio Reactant – Transition State Structure – Product 1.Selection of the theoretical model 2.Geometry optimization 3.Frequency calculation 4.Energy.

1 MODELING MATTER AT NANOSCALES 6.The theory of molecular orbitals for the description of nanosystems (part II) Ab initio methods. Basis functions.

Chemistry 700 Lectures. Resources Grant and Richards, Foresman and Frisch, Exploring Chemistry with Electronic Structure Methods (Gaussian Inc., 1996)

Electric field which acts on core C due to the valence electrons and the other cores. Where is a cutoff function for the electric field inside the core.

Antal Zoltan-PhD candidate 6304-Computational Chemistry March 2010.

Quantum Methods For Adsorption

1 MODELING MATTER AT NANOSCALES 6. The theory of molecular orbitals for the description of nanosystems (part II) Perturbational methods for dealing.

0 Jack SimonsJack Simons, Henry Eyring Scientist and Professor Chemistry Department University of Utah Electronic Structure Theory Session 5.

Lecture 5. Many-Electron Atoms. Pt

Multiply Charged Ions Quantum Chemical Computations Trento, May 2002 Lecture 2.

Lecture 11. Basis Functions & Basis Set

Lecture 8. Chemical Bonding

Quantum Chemistry in Molecular Modeling: Our Agenda Postulates, Schrödinger equation & examples (Ch. 2-8) Computational chemistry (Ch. 16) Hydrogen-like.

Molecular quantum mechanics - electron has cartesian and spin coordinates one electron functions one electron functions - no spin operator in electronic.

MODELING MATTER AT NANOSCALES 4. Introduction to quantum treatments Eigenvectors and eigenvalues of a matrix.

2/09/2015PHY 752 Spring Lecture 111 PHY 752 Solid State Physics 11-11:50 AM MWF Olin 107 Plan for Lecture 11: Reading: Chapter 9 in MPM Approximations.

Advanced methods of molecular dynamics 1.Monte Carlo methods 2.Free energy calculations 3.Ab initio molecular dynamics 4.Quantum molecular dynamics 5.Trajectory.

Dissociation of H 2 Do HF calculations for different values of the H-H internuclear distance (this distance is fixed since we are in the Born- Oppenheimer.

Basics of Quantum Chemistry Todd J. Martinez. “Conventional” Quantum Chemistry Is DFT the end of the story? No! Even the best DFT often yield errors of.

©2011, Jordan, Schmidt & Kable Lecture 13 Lecture 13 Self-consistent field theory This is how we do it.

Lecture 9. Many-Electron Atoms

Computational Physics (Lecture 22) PHY4061. In 1965, Mermin extended the Hohenberg-Kohn arguments to finite temperature canonical and grand canonical.

Ch.1. Elementary Quantum Chemistry

Quantum Mechanics José R. Valverde EMBnet/CNB © José R. Valverde, 2014 CC-BY-NC-SA.

Structure of Presentation

Molecular Models.

Statistical Mechanics and Multi-Scale Simulation Methods ChBE

Experiments show O2 is paramagnetic

Molecular Orbital Methods

Valence Shell Electron Pair Repulsion

Presentation transcript:

A Walkthrough For Quantum Chemistry Newbies Part 1: Basis Sets, Related Functions, and Usage by Peker Milas

Exact H Wave Functions Question 1: Why do we need approximated basis sets ??? Fig:

Fig:

Answer 1: Even if we use H like wave functions for each atom in a molecule, we will have a big problem in computations…. Question 2: How can we treat electronic structure of a molecule ??? Answer 2a: First we need to simplify our molecule by thinking of electrons can not interact wit each other. We call this Hartree-Fock Method… Answer 2b: Second, we can write down total electronic part of Hamiltonian as a single Slater determinant or as a product of one-electron wave functions… But, to proceed we need to make a guess for electron wave functions…

So, We have Basis Sets… Basis Sets Minimal Basis Sets STO-nG Pople Basis Sets X-YZG X-YZWG Correlation-Consistent Basis Sets cc-pVDZ cc-pVTZ cc-pVQZ Other Basis Sets DZV TZV Ref: Split Valence Basis Sets

STO-nG, Minimal Basis Set… First developed by J.C. Slater, STO ~ Slater Type Orbitals… All orbitals are sum of gaussians up to some constants in front of them… All orbitals are treated as same… They are simplest basis sets and suitable for large molecules… They have extended versions as double, triple, quadruple zeta… S. F. Boys came up with Example STO-3G Basis Set (Extended Triple Zeta)… Ref 1: Ref 2:

X-YZG, Pople Basis Set… First proposed by J. Pople… Inner orbitals and valence orbitals are treated different… With X-YZG* and ** p to s and s to p polarizations are included… With X-YZ+G and ++ p to s and s to p diffusions are included… With X-YZWG valence orbitals can be extended… They are relatively easy to calculate…

cc-pVDZ, etc…, Correlation-Consistent Basis Sets… Developed by Dunning and coworkers… A more realistic treatment of molecular orbitals… cc-p stands for correlation-consistent polarized… V stands for valence only basis set… DZ, double zeta… Widely used for post-Hartree-Fock calculations…

Some ongoing calculations and results… First step of geometry optimization for Cy3 has finished… 6-31G Basis Set has been utilized… Slater Determinant solved numerically without any approximations… Good news… Optimization converged smoothly… Equilibrium geometry can be utilized for next calculation with new Basis Set 6-31G(d) or equivalently 6-31G*…

Bad news… Optimization should be carried at least up to 6-31G*… Optimization with 6-31G* basis should converge for calculation of RESP charges… Firefly/PcGamess couldn’t finish optimization because of memory shortages… A new level of approximation (either ab inito or DFT) should be applied… Possible calculation ways… DFT with BLY3P type electron correlation functional… Ab inito with Moller-Plesset lvl 2 perturbation Theory (MP2)… As a last resort; cc-pVDZ type post Hartree-Fock method…

Thank you…