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, ...).
1,573
questions
-1
votes
1
answer
64
views
Why do we only use the principal quantum number to calculate the energy of an electron in an H atom?
According to my high school textbook the energy of an electron in a hydrogen atom is $E = -13.6/n^2~\pu{eV}$, where $n$ is the principal quantum number of the orbital in which the electron is present.
...
-4
votes
0
answers
27
views
off-resonance Raman and normal Raman spectra [closed]
What is the difference between the off-resonance Raman and normal Raman spectra in gaussian? How to calculate the off-resonance Raman spectra in gaussian?
- 1
1
vote
0
answers
22
views
Gaussian Program Error for Linear Triatomic Molecule
I am trying to calculate the Hessian and vibrational frequencies of OCS (and eventually some anharmonic properties) with Gaussian09. However, the program always fails and I end up with the following ...
- 111
-4
votes
0
answers
36
views
Raman and IR spectra [closed]
Can anybody tell me that how actually the Raman and IR spectrum calculates in DFT calculations?
I am not asking about the keyword. I want to know the principle that how X Y Z cartesian coordinates ...
- 1
2
votes
1
answer
201
views
Why d orbitals oriented along $z^2$ axis assigned zero magnetic quantum number?
I have been studying quantum mechanics recently and I have come across this:
d orbitals oriented along the $z^2$ axis is assigned zero magnetic quantum number
I am wondering why specifically the $dz^...
- 212
0
votes
1
answer
45
views
Why we seldon use Fermi Surfaces to explain chemical behaviour? [closed]
Chemistry basically involves studying the behavior of electrons in atoms and their consequences. Solid-state physicists deeply study Fermi surfaces, analyzing the three-dimensional behavior of atoms. ...
- 124
-1
votes
0
answers
28
views
Sushells vs Orbitals...A visual distinction [duplicate]
Is there any coherent visual diagram that might explain how orbitals and subshells co exist in the same shell? I'm unable to find any online, except for those which indicate only orbitals as dense ...
-1
votes
0
answers
46
views
Why is the covalent radii of carbon significantly smaller than that of boron, and why do metals have more significant changes in radii
I’m currently looking at this graph of the 2nd-period covalent radii, and it seems like moving from boron to carbon, there is a more significant decrease compared to moving across the rest of the ...
- 59
2
votes
0
answers
31
views
Is the $2p$ RPD defined along the z-axis?
In MIT $5.111$ class (lecture $6$), we are to compare the most probable radius of a $2s$ orbital and a $2p$ orbital. The graph used by the professor represents the RPD versus $r$:
My question is: in ...
- 219
1
vote
0
answers
31
views
Doubly occupied orbitals in quantum chemistry? (openfermion.org)
I am interested in diagonalising the fermionic Hamiltonian of small molecules, such as LiH in second quantisation.
The Hamiltonian is
\begin{align}
H(R) = \sum_{ij} h_{ij}(R) a_i^\dagger a_j + \frac{1}...
- 111
1
vote
0
answers
67
views
Finding the relative position of the molecule in the adsorbate and adsorbent by minimizing the Hamiltonian
I am trying to model an adsorbing process (or more precisely, Heterogeneous catalysis process between solid catalyst and gas reactants). One of the step is to minimize the Hamiltonian by optimizing ...
- 77
1
vote
1
answer
56
views
Do Electron-Withdrawing-Groups give an hypsochromic shift or a bathochromic one? and why?
I'm not familiar with this topic,but i know that bathochromic shifts occur when the energy gap between energy levels of the substituted molecule, are lower than the unsubstituted one;viceversa ...
- 21
1
vote
0
answers
51
views
Absurd result for the selection rules in the three-dimensional PIB
By using time-dependent perturbation theory and some simplifying assumptions, we know that a transition for a charged particle $q$ from a quantum-mechanical state $m$ to $n$ is allowed if and only if
\...
- 3,671
1
vote
0
answers
68
views
In the RDF plot of a particular orbital, why don't peaks come with radius greater than that of the max peak?
While studying radial distribution function (RDF) plots I see that orbitals (3s, 2s, ... 3p etc) often have peaks at radii less than that of the maximum peak. Assuming the probability of finding an e-...
2
votes
0
answers
56
views
Why is the translational motion left out of the energy eigenvalue in the hydrogen atom?
When solving the hydrogen atom, since we have two particles, the wave function has the form $\psi(\mathbf{q}_1,\mathbf{q}_2)$. Generally, textbooks proceed to demonstrate that an interacting two-...
- 3,671