Questions tagged [quantum-chemistry]
Quantum chemistry is a subfield of quantum mechanics. Like its parent field, quantum chemistry focuses on understanding physical phenomena occuring at the atomic scale. Quantum chemistry however is more focused on providing useful descriptions of electronic structure to aid in understanding chemical problems (e.g. reactions, spectra, dynamics, ...).
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Why is the statement regarding the strength of ionic bonds reasonable? [closed]
In largely ionic compounds (e.g. NaBr and NaI), it seems to be generally true that, the greater the differences of electronegativity between the forming substances (i.e. The compound has more "...
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Band structure of solids in general
As my last question (Semiconductors and their electronic bands) was badly structured, I decided to elaborate my questions a bit.
As I now know, every solid/liquid forms a band structure, so all ...
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What can be inferred from overlap matrix S if coefficient matrix C is unitary in Roothaan equation?
I was going through the Hartree-Fock algorithm, transforming the spatial molecular orbitals {$\psi _i$} to be a linear combination of Roothaan basis set {$\phi_i$}. From my knowledge {$\psi_i$} is set ...
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Effective Core Potentials and their "corresponding Pople" basis set
Reading through a handout from Yale shows the author correlating the ECP with Pople basis sets. The author of this says the corresponding basis set for SDD is 6-31G, Def2TZV as 6-311G, LANL2MB as STO-...
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Why is cyclohexane more polarizable than benzene?
Looking at figure 4.2 here, we can see experimentaly that cyclohexane is more polarizable than benzene.
Why is this the case?
Intuitively, I would think that because the orbitals in benzene are more ...
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Term symbols in transition metals and lanthanides
Hello I was researching a little about term symbols of lanthanides and transition metals and have got two questions.
It is known that lanthanides don’t follow LS-coupling, but instead JJ-coupling. ...
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How can I calculate the electrostatic energy between two fragments?
I have a 2-fragment molecular complex with partial charge transfer from fragment 1 to fragment 2. The binding energy is ~0.3 eV and I want to evaluate what fraction comes from electrostatic attraction....
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Eigenfunctions of total angular momenta as linear combinations of Slater-determinants
In the Hartree scheme for many-electron atoms, the approximated Hamiltonian (in a.u.)
$$\hat{H} = \sum_{i=1}^Z \left(-\frac{1}{2} \nabla_i^2 -\frac{Z}{r_i} + V_\text{H}\left(r_i\right)\right)$$
is ...
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Quantum chemistry and covalent bonding
How can the formation of a covalent bond be described from a quantum perspective, and what implications does it have for traditional chemical bonding theory?
Specifically, in the context of many-...
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Reduction of direct product representation
When we do the reduction of the reducible representation generated from the total wavefunction expressed as product of MOs of appropriate symmetry, we can find the direct sum of more than one ...
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Group theory and exact Eigenfunctions of Hamiltonian
I think I've understand why the real Eigenfunctions of Hamiltonian belong to a given irreducible representation and I've read that also MOs have to transform as irreducible representation due to the ...
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What does the 2 in t2g stand for?
I have read so far that it is about whether the d-Orbital is symmetric to a C2 element perpendicular to its main rotational axis. If all the given orbitals in a group are symmetric to that element, ...
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Commutating operators of angular momenta
I've studied the formal procedure to pass from the uncoupled basis set of individual angular momenta to the coupled basis set of total angular momenta for polyelectronic atoms.
I start from an ...
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Why don't I get a whole number when determining the vibrational energy level of F2? [closed]
This is a cross post from physics stackexchange. I hope to get more answers here, because I think chemists have more to do with such things.
So I was playing around with some data and formulas and ...
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Electron energy shells/ levels
Essentially, I am told electron shell closest to the nucleus is the lowest energy level and subsequent shells have higher energy (I.e. those further from the nucleus).
But..... electrons in the ...
