Linked Questions

25
votes
3answers
2k views

A comprehensive list of theoretical approximations that are used in computational chemistry

I am having trouble recognizing all the approximations that are used in computational chemistry. I would like to start an answer list (similar as to the list of resources for learning chemistry) that ...
14
votes
2answers
2k views

How do I make 3d molecular graphics similar to those shown on Wikipedia?

I want to make 3d molecular graphics similar to those found on Wikipedia. In the page for benzene, you can see the structure looks like this: However, if I go to the interactive image as shown in ...
14
votes
4answers
4k views

Restricted open-shell versus unrestricted methods for open shell systems

Open-Shell systems (radicals and so on) can be modeled by single-determinant quantum chemical methods using unrestricted (u) or restricted open-shell (ro) methods (I am aware that single-determinant ...
12
votes
1answer
386 views

Books for a very advanced 3rd grader (elementary school) [duplicate]

My daughter is a 3rd grader, but she reads at 8th grade level, and she is 2 grade levels ahead in math. She reads everything she gets her hands on. She took some chemistry activities, and she loved ...
11
votes
2answers
679 views

Is the notion of orbitals different in theoretical chemistry?

I am just an average chemistry student that is currently exposed to theoretical chemistry. And I am seeing very puzzling things, such as 1p, 2f, 3g orbitals. In my attempt to reconcile this, I was ...
10
votes
4answers
563 views

Stability of 4-pyridone vs 4-pyridinol

In kryptomerism assignment, there was a question to compare more stable tautomeric form between 4-pyridone (1) and 4-pyridinol (2): Answer: 4-pyridone. My friend gave two plausible reasons: $\ce{C=...
9
votes
1answer
6k views

Why isn't the orbital angular momentum also considered while calculating the magnetic moments 3d transition elements?

My textbook (Chapter: The d- and f- Block Elements) makes an interesting assertion, however, without any reason to back it up. Paramagnetism arises from the presence of unpaired electons, each such ...
9
votes
1answer
424 views

Is it possible to calculate the momentum of an electron precisely?

In a national level, undergraduate examination (TIFR-2018) following question was asked: Which of the following is not correct with regard to the uncertainty principle? An electron in an atom cannot ...
8
votes
1answer
352 views

What are introductory level books on chemical engineering?

I'm currently enrolled in a chemical engineering course in my college, and in my first year, I'd like to get a nice introductory book on that field of study. I'd prefer that the book covers several ...
8
votes
1answer
292 views

Szabo and Ostlund's calculation of repulsion integral on page 172 via A.41

Returning to Szabo & Ostlund after a hiatus I tried to recreate his STO-3G calculation for HeH+ which begins on p. 168. It all went fine except for the two-electron, two-center integrals. I ...
7
votes
1answer
364 views

What is the correct approach to obtain PES using CASSCF?

I am new to CASSCF. I want to draw a PES for the ground state and the first excited sate of methyl amine for learning purpose. I want to verify if I am correct using the correct approach. Do a ...
7
votes
1answer
173 views

My Misconception of Entropy

It was recently brought to my attention that my understanding of entropy is wonky at best. In my experience, entropy was introduced (superficially at best) during general chemistry/foundations of ...
6
votes
0answers
125 views

Is there any book as Landau's for Physics but for Chemistry? [closed]

Landau's series of books are a collection of books that describe briefly but very deeply the core part of the main fields of Physics. He wrote them rigorously and they are very very abstract. He gave ...
5
votes
2answers
96 views

Why are excess nuclei required to produce an NMR signal?

In NMR, an excess population of nuclei is required to produce a signal. If saturation is achieved (same number of nuclei in the α and β states) no net signal can be produced. A signal is produced when ...
5
votes
1answer
92 views

Global reactivity parameters from open shell DFT calculations using Koopman's theorem

Koopmans' theorem is a useful approach to calculate the global reactivity parameters from the HOMO-LUMO energies. My question is, does it apply to the open-shell systems where we get two sets of ...

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