- Видео 33
- Просмотров 247 534
David Sherrill
Добавлен 21 сен 2009
Computational Quantum Chemistry. Machine Learning. And Cats.
The Hartree-Fock Algorithm
I discuss how the Hartree-Fock algorithm works. First I review the Hartree-Fock equations, then I give an outline of the steps of the Hartree-Fock algorithm, and then I discuss the basics of how these steps would be implemented on a computer.
Просмотров: 8 467
Видео
Introduction to Electron Spin Part 2
Просмотров 2,5 тыс.3 года назад
I discuss some more complicated examples of determining electron spin: transition-metal complexes, and diradicals. I also explain what an open-shell singlet is, and how it's important for modeling excited electronic states (and for some ground states). We conclude the introduction to Spin by talking about spin eigenfunctions, and spin contamination in UHF computations.
Introduction to Electron Spin Part 1
Просмотров 7 тыс.3 года назад
I provide a basic introduction to electron spin, and how to determine the spin quantum number S and its projection on the z-axis, Ms, for an atom or molecule in simple situations. I also introduce the *spin multiplicity* (2S 1), which is the value that the user has to input into quantum chemistry programs.
Orbitals and Electron Configurations Part 2
Просмотров 2,7 тыс.3 года назад
I discuss orbitals and electron configurations for diatomic molecules, and generalizations to polyatomic molecules
Orbitals and Electron Configurations Part 1
Просмотров 2,9 тыс.3 года назад
I review the qualitative form of the H atom orbitals, and how to get atomic electron configurations using the Aufbau principle
Basis Sets part 2
Просмотров 10 тыс.3 года назад
We discuss several popular basis sets, and briefly discuss how the basis set size affects the quality of quantum chemistry computations
Basis Sets part 1
Просмотров 23 тыс.3 года назад
We discuss one-electron ("atomic orbital") basis sets in quantum chemistry: Slater-type orbitals, Gaussian-type orbitals, and contracted Gaussian-type orbitals.
Introduction to Hartree-Fock Molecular Orbital Theory Part 3
Просмотров 8 тыс.3 года назад
We discuss the Hartree-Fock equations, the Hartree-Fock algorithm, orbital energies, and practical considerations
Introduction to Hartree-Fock Molecular Orbital Theory Part 2
Просмотров 11 тыс.3 года назад
We discuss spin integration, restricted Hartree-Fock (RHF), unrestricted Hartree-Fock (UHF), and the pseudo-classical interpretation of the Hartree-Fock energies
Research in the Sherrill group
Просмотров 1,5 тыс.3 года назад
I briefly describe topics of interest to my research group
Introduction to Hartree-Fock Molecular Orbital Theory Part 1
Просмотров 24 тыс.3 года назад
This video introduces the theory behind Hartree-Fock Molecular Orbital theory, starting from the assumption of the Born-Oppenheimer approximation and the form of the electronic Hamiltonian, to the assumption of a single Slater determinant, to the Hartree-Fock energy expression that we minimize when applying the variational method.
Intro to Electronic Structure Theory Part 3
Просмотров 6 тыс.3 года назад
Our introduction to electronic structure theory concludes with a brief introduction to Hartree-Fock Molecular Orbital theory, semi-empirical methods, Density Functional Theory, and electron correlation methods
Intro to Electronic Structure Theory Part 2
Просмотров 6 тыс.3 года назад
We discuss the Born-Oppenheimer approximation and potential energy surfaces
Intro to Electronic Structure Theory Part 1
Просмотров 7 тыс.3 года назад
I introduce Electronic Structure Theory, also known as Quantum Chemistry
Introduction to Key Concepts from Quantum Mechanics for Beginning Computational Chemists
Просмотров 5 тыс.3 года назад
Many beginners in computational chemistry don't have much background in quantum mechanics. This video introduces some of the key concepts and definitions.
Molecular Simulations Part 2: Properties and Algorithms
Просмотров 5 тыс.3 года назад
Molecular Simulations Part 2: Properties and Algorithms
Molecular Simulations Part 1: Molecular Dynamics and Monte Carlo
Просмотров 15 тыс.3 года назад
Molecular Simulations Part 1: Molecular Dynamics and Monte Carlo
Introduction to Molecular Mechanics Part 4: Cross Terms Accuracy and QM/MM
Просмотров 2,6 тыс.3 года назад
Introduction to Molecular Mechanics Part 4: Cross Terms Accuracy and QM/MM
Introduction to Molecular Mechanics Part 3: Advanced Electrostatics and Polarization
Просмотров 3,1 тыс.3 года назад
Introduction to Molecular Mechanics Part 3: Advanced Electrostatics and Polarization
Introduction to Molecular Mechanics Part 2: Nonbonded Terms
Просмотров 5 тыс.3 года назад
Introduction to Molecular Mechanics Part 2: Nonbonded Terms
Introduction to Molecular Mechanics Part 1: Stretch, Bend, and Torsion Terms
Просмотров 19 тыс.3 года назад
Introduction to Molecular Mechanics Part 1: Stretch, Bend, and Torsion Terms
National Chemistry Week Demo: Precipitates
Просмотров 1654 года назад
National Chemistry Week Demo: Precipitates
National Chemistry Week Demos: pH of household items
Просмотров 2654 года назад
National Chemistry Week Demos: pH of household items
National Chemistry Week Demo: Electrolytes
Просмотров 1804 года назад
National Chemistry Week Demo: Electrolytes
Semiempirical Methods in Quantum Chemistry
Просмотров 4,4 тыс.4 года назад
Semiempirical Methods in Quantum Chemistry
Non-Dynamical (Static) Electron Correlation: Bond Breaking in Quantum Chemistry
Просмотров 3,5 тыс.4 года назад
Non-Dynamical (Static) Electron Correlation: Bond Breaking in Quantum Chemistry
Excited Electronic States in Quantum Chemistry
Просмотров 9 тыс.4 года назад
Excited Electronic States in Quantum Chemistry
Practical Advice for Quantum Chemistry Computations
Просмотров 6 тыс.4 года назад
Practical Advice for Quantum Chemistry Computations
Introduction to Density Functional Theory (DFT)
Просмотров 31 тыс.4 года назад
Introduction to Density Functional Theory (DFT)
searched for dft, came for the cat, stayed for hoping to see the cat again
Oh my god, thats where hunds rules come from!!! Ahaha I love how the more you study chemistry the more everything connects!
Very nicely presented, Professor. Thank you very much.
thank you so much for this video! I have found this three years apart from when it was uploaded, but it helped me a lot to know about the scientific terms and be able to learn them in order !
best explanation, great job.
Fantastic explanation, thanks a bunch!
Hello, Professor! Thank you for an insightful lecture! I have a couple of questions: 1) How exactly close in energy a pair of determinants must be to require multireference treatment? Is there a way to know this on a case-by-case basis? 2) In the example of double bond rotation (fig. 2 from your 1998 paper) what makes the two degenerate configurations, representing the TS, different? In the case of H2, the bonding and antibonding orbitals represented two qualitatively different ways for electrons to populate the space around the nuclei, but in the ethene case I don't see how the two presented orbitals differ qualitatively. In other words, how is that we are missing some electron density in some parts of the TS if we include only one configuration but not the other? 3) In the case of bond dissiciation in polar condensed phase (e.g. HF in water becomes H+ and F-) it seems to me that ionic contributions from RHF treatment are actually required to describe bond heterolysis. On the other hand, the covalent terms seem to be irrelevant. So, do I understand correctly that in case of heterolysis RHF error comes from covalent terms (besides the dynamic correlation part), the opposite of H2 dissociation in vacuum?
Hi excition, 1) there's not a well-accepted rule for this. Usually people pay more attention to the weights of the determinants in a preliminary calculation, and anything with a coefficient ~0.2 or more will look pretty important. 2) IIRC, those two configurations in ethylene also look very different away from the TS ... they are pi^2 and pi*^2 3) yeah my example and usual explanations about multireference character are about gas-phase examples. In solution, I agree you would expect the H+ + F- solution to get massively stabilized in energy. However, I strongly suspect that in the bond-breaking region (as you are starting to pull apart the bond), both the homolytic and heterolytic electron configurations contribute strongly to the full wavefunction, meaning a multi-reference approach is in principle needed in gas or solution phase. I'm not sure if it would be true to say that the error in solution would be mainly driven by the covalent terms.
@@DavidSherrill1 Thank you for your reply! 1) I guess I wanted to ask a different question. How does one know that static correlation is important for a given systemn without doing something costly like CCSD T1-diagnostic? Is it just experience? 2) I see how pi*^2 can add some electron density in a different manner than pi^2 at some point of PES near the TS. As you showed, this changes the shape of the PES from being cusp-like to a more round shape. However, if don't understand how pi*^2 can change the electron density at the TS. The two configurations look identical at the TS. In other words, how including the pi*^2 configuration in our reference lowers the total energy of the TS when compared to RHF?
@@unbridled_exciton Yeah, sometimes experience is sufficient to know something is going to have strong multireference character (unimolecular bond breaking reactions, diradicals, partially-filled d shells with small energy gaps between relevant orbitals, etc.). Other times it's not so obvious and an examination of the T1 diagnostic, largest T2 amplitude, etc. are needed. Regarding your second question, as I recall, yes, the two configurations do look identical at the TS ... they probably both belong to a doubly-degenerate irrep or something. I tend to look at wavefunctions more than densities, so it doesn't bother me that the density from each configuration individually might look the same.
@@DavidSherrill1 Thank you for your time!
This is really the video that I'm looking for! Thank you very much! 😊
Isn't bond energy = 0.5×k(θ-θeq)^2 Why have U used E= k((θ-θeq)^2
Just depends on whether 1/2 has been absorbed into the constant k or not
@@DavidSherrill1 thank
Shouldn't (m_s)_1h be equal to -h/2 here 21:26?
Just starting in chemistry on my own and i have some background in ml/ds/cs. This is such a good intro to these methods. Thank you.
omg I loved it, thank u so much, I learned a lot, the cat is amazing
Greetings from Taiwan! Since I've been working with the OPLS force field recently, it's been really insightful to understand what those parameters represent. The approaches used in force field methods have been very inspiring. Thank you for your great effort!
goooood
thank you so much!!!
Thank you this is amaIng
Thank you so much for the Notes on building D at 37:00 . I was writing my own RHF program for learning and tried using the number of basis functions instead of electrons. This is the first source I found where it's made clear to use the number of electrons. Im eternally grateful to you, for saving me porbably multiple additional days of debugging!
Thank you very much for this explanation. is it possible to have the slides?
Thank you so much for giving us that wonderful explanation.
Thank you, professor.
Great class, professor.
Thank you very much for your videos Professor!! They are so good!
18:00 slide dialectrics, fwiw:) 27:00, further -> farther?
This is akin to the high dimensional optimization done every 5 minutes to determine real time dispatch of generators on the grid. N ~ 6000-15000. I’m new to this- it’s very cool. Are the governing eqns close to linear?
SVD baby!
Thank you for the very helpful video, this is the best explanation I found to get an introduction to computational chemistry as a chemistry student. Good job 👍
sir when i calculated rdf by lammps the peak for some atoms are very high especially for those atoms which concentration is low, sir how i could decrease the peak value. thank you so much sir
Hello sir, thank you for this explanatory lectures on Computational Chemistry which I needed a lot. May I ask which sources did you used as a text book for example while preparing these lectures?
A lot of the material is in Szabo and Ostlund's Modern Quantum Chemistry, and in Frank Jensen's Introduction to Computational Chemistry
good job, I'm not verry good in English🤣🤣🤣🤣🤣🤣 but I try to understand and all thing understanble....great
Thank you for the lecture. It really means a lot
Thank you for the nice lecture!
Excellent :)
Thank you very much!!!
These are the best videos on electronic structure theory that I have found. Very clear and helpful for a physics person moving into chemistry.
Why you quit physics???
@@zishangwu1916 So i can do more statistical mechanics bro
I love your videos you're always so humble, sincere and helpful. I love your cat its so cute, such a rompy little one :))
Thanks for the lecture professor I have two questions. 1) is it only applicable for ground state only . 2) in the term of when you said it's an exact theory but it's exchange correlation energy functional if that's the issue here so can we just “ignore” it since it's very small term and the remaining term can be treated as by average value of them as Born Oppenheimer approximation. I hope it make sense
Professor, I'm in my second research project as an undegraduate here in USP, Brasil; and I've watched your videos since day zero. Thanks a lot for all your knowledge and your will to share it. You're an incredible teacher!
Cat
How can physicists discount that an electron can spin around its own axis when, in fact, it has mass? How did they come to the conclusion that spinning is not something electrons do? No physicist has explained this point of view.
$\vec{r}^{\mkern3mu\prime}$ will help with overlapping of prime symbol and the arrow symbol.
Thank you Prof. Sherrill on the excellent explanation of the HF Theory! You covered almost all the relevant questions that popped into my head which made it a very clear lecture! I had a hard time understanding this from my own professor here in austria, so thank you very much!
OMG.!! Thank u so much for those lectures.!!! I can't understand it in books !!
I'm here for the cat.
Watching your videos to prepare…because I hope they can waive the calculus 2 prerequisite and let me into the atomic theory class at my school!!
the quantum cat ..!!
Please give some about free software for QM/MM calculation for academic purposes
I heard someone mention hartree-fock so I looked it up on youtube and found this video. I have no foundation for any of this stuff so I have no idea what's going on. I have so much to learn before I can understand this...
go jackets
Thanks a lot sir...this helped a lot
Can you recommend a textbook that would be good for beginners that are starting computational chemistry research?