13 votes

Bond length from infrared spectra?

A partial list of bond lengths I have determined from IR spectra over my career: \begin{array}{ccc} \rm{Molecule} & \rm{Bond ~Length ~ (picometers)} & \rm{References}\\ \hline \ce{Li_2}(1^1\...
I have no free time anymore's user avatar
12 votes
Accepted

Bond Order: When and how is it used today?

Why Bond Order? Bond order isn't terribly useful to a computationalist directly; however, it can be invaluable for translating Quantum Mechanical results into a framework thats readily understood by ...
Tyberius's user avatar
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11 votes

Bond length from infrared spectra?

This is a task suited to single crystal XRD. This does require you to be able to form a crystal of your substance which can be difficult at times but this allows for potentially high accuracy of bond ...
Tristan Maxson's user avatar
11 votes

What are the types of bond orders?

Wiberg (1968) Let's start with the "classic" bond order paper by Ken Wiberg (born in 1927 and still alive!). The Wiberg Bond Index (WBI) between fragments A and B of AB is calculated as ...
I have no free time anymore's user avatar
11 votes

Bond length from infrared spectra?

I agree with all answers provided so far: you cannot quantitatively deduce bond lengths from infrared spectra. However, see the answer by Nike Dattani about the inverse, predicting IR spectra from ...
ProfM's user avatar
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9 votes

Bond length from infrared spectra?

Addendum: While the method described below is commonly used by experimentalists, I was mistaken that IR spectrum could not be used to obtain bond lengths. Nike's answer does a great job explaining how ...
Tyberius's user avatar
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8 votes

What are the types of bond orders?

How to test bond order methods for chemical consistency Some of the bond order methods that claim to work do not give consistent results across different SZ values of a spin multiplet or different ...
Thomas Manz's user avatar
8 votes

What are the types of bond orders?

Laplacian Bond Order This method is an extension of the QTAIM (Quantum Theory of Atoms In Molecules) concept of using the Laplacian of the electron density $\nabla^2\rho$ to characterize bonding. ...
Tyberius's user avatar
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8 votes

What are the types of bond orders?

It depends on what you want from it. If you're an organic chemist, you'd be mostly interested in the type of bond (single, double, triple, aromatic), and for that the bond order is most relevant (but ...
MSwart's user avatar
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7 votes

Bond Order: When and how is it used today?

I disagree with the statement by Tyberius that: "Bond order isn't terribly useful to a computationalist directly; however, it can be invaluable for translating Quantum Mechanical results into a ...
Thomas Manz's user avatar
7 votes

How to understand the formation of covalent bond from the viewpoint of wavefunction interaction?

There is more than one way to answer this question well. I'll give one answer here. Let's treat the two atoms (that will form a covalent bond) as two localized election states (orbitals). The detailed ...
taciteloquence's user avatar
7 votes

Are there any programs that can do non-orthogonal CI?

To start with, we do have: LUCIA, a Correlation Program, 2019, developed by Kähler and Olsen. Nonorthogonal internally contracted multi-configurational perturbation theory and Dynamic correlation for ...
Meilani Wibowo's user avatar
6 votes

Bond Order: When and how is it used today?

An interesting application of bond orders in reactive molecular dynamics simulations is the ReaxFF force field, where the MD force field parameters are optimized by ab initio simulations. To quote one ...
Arc's user avatar
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6 votes

Bond length from infrared spectra?

I am surprised no-one above mentions the classic textbook example of the IR spectrum of HCl gas, which shows rather beautiful rotational structure superimposed on the vibrational band. The spacing of ...
Ian's user avatar
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3 votes
Accepted

Valence correction by adding formal charge in RDKit

After some investigation, I don't think it's possible to add formal charge posthoc without modeling hydrogens explicitly. Here is an example to illustrate: Consider both molecules ...
Njw96's user avatar
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2 votes
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Are frozen-core approximations for the elements of first or second row accurate for potentially extremely short bond distances present in the molecule

Due to the errors associated with your choice of functional (even if it's a double hybrid functional), I think there is not much value in unfreezing the core with regards to getting more accurate ...
I have no free time anymore's user avatar

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