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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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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....
Nick Kateris's user avatar
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271 views

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 ...
Simone's user avatar
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1 answer
180 views

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 ...
Chemistry.'s user avatar
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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 ...
Chemistry.'s user avatar
2 votes
2 answers
477 views

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, ...
Rivinius's user avatar
2 votes
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41 views

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 ...
Chemistry.'s user avatar
1 vote
2 answers
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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 ...
iwab's user avatar
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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 ...
Elaine Gerrard's user avatar
6 votes
1 answer
135 views

"Probability flux": Imaginary part

I was confronted with this problem from "Mathematik für Chemiker", 8th edition (Ansgar Jüngel, Hans G. Zachmann): $$ \begin{align} \partial_t |\psi|^2 &= \partial_t (\bar\psi\psi) \\ &...
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Some advice on inorganic textbook [duplicate]

I'd like to have some advice on Inorganic textbooks. I've already consulted some books (Kettle, Drago, Keiter, Cotton) and they are all very useful, but now I'm searching for a textbook which focuses ...
Chemistry.'s user avatar
-2 votes
1 answer
97 views

Doubt on vibronic transitions

When we justify the presence of electronic transitions forbidden by Laporte selection rule, the coupling between electronic and vibrational states help us. Why we say that in this way we are ...
Chemistry.'s user avatar
4 votes
1 answer
274 views

Principal quantum number and 'good' quantum numbers

When we discuss about configurations we specify n, l, m quantum numbers for the individual electrons. My question is: why when we pass from configurations to atomic terms in order to use the total ...
Chemistry.'s user avatar
1 vote
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64 views

Hartree-Fock calculations of the states of Nitrogen molecule ion

I was reading the third chapter of "Modern Quantum Chemistry" by A. Szabo and N. Ostlund about HF calculations, and in the end of the chapter it shows as an example a calculation on $\ce{N2}$...
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Why is there a point of orbits along with quantization in case of energy gaps?

As per my textbook and online sources. The definition of Energy bands I have found is this: A) Energy levels: ( In a simplified view of an electronic structure of a single atom or isolated molecule. ...
Srijan's user avatar
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1 answer
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Refrence on shielding effect vs inter electronic repulsion

Recently I came across a very interesting concept , some scholars were saying that - Shielding accounts just one component (radial) of interelectronic repulsion not complete repulsion Who they are - ...
Bharat Prajapat's user avatar
3 votes
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90 views

Fluorescence and resulting vibrational state

I was taking a look at Jablonski schemes and had some doubts regarding it. Now assume a regular molecule which follows this Jablonski scheme: We can see that when molecules absorb certain quantized ...
Mäßige's user avatar
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2 answers
298 views

electron - electron repulsion and shielding effect [closed]

What is difference between shielding and electron electron repulsion. When I read this article , I came to know that both are different. First Read this paragraph and see the graph of ionization ...
Govind Prajapat's user avatar
-1 votes
1 answer
284 views

Ionization and exchange energy [closed]

As we all know that 'Nitrogen' has higher 'Ionization Energy' than its neighboring elements both carbon and oxygen, opposite to the trend of increasing ionization energy across a period. The reason ...
Govind Prajapat's user avatar
-2 votes
2 answers
87 views

Are the inner circular rings in higher 's' sub shells part of inner 's' sub shells, as the diagrams suggests?

The diagram of, for example, 2s and 3s, is the innermost circle showing electron probability has to be 1s subshell. How could it be the part of 2s or 3s, since it is a complete circle around nucleus ...
Mohammed Hamza's user avatar
2 votes
1 answer
203 views

How do the orbitals in atoms synchronize their phases during the formation of a bond?

Suppose I have two hydrogen atoms, each with one electron in their 1s orbital. Then we can represent the wave functions of these two as say $|\Psi\rangle_1$ and $|\Psi\rangle_2$ for each of the two ...
Hadi Khan's user avatar
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9 votes
2 answers
390 views

Software to draw one-dimensional PES including vibrational energy levels

I am trying to represent the difference between the an anharmonic and harmonic treatment of vibrations. The easiest way to do this is to present an example of a harmonic and anharmonic potential ...
isolated matrix's user avatar
3 votes
0 answers
66 views

Can excited electronic states also decay due to collisions?

I was wondering if electronic states could decay due to collisions and not by fluorescence? Just like vibronic relaxations can happen, when vibrationally excited molecules can lose those extra modes ...
Mäßige's user avatar
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4 votes
1 answer
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Deriving the equation of motion for adiabatic approximation

In the textbook, Theories of Molecular Reaction Dyanmics by Flemming Y. Hansen and Niels E. Henriksen, there is a derivation of the equation of motion for the adiabatic approximation (pgs. 5-7). The ...
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1 answer
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How Can the First Ionization Energy of Helium be Accurately Calculated Using Basic Quantum Mechanics?

How Can the First Ionization Energy of Helium be Accurately Calculated Using Basic Quantum Mechanics? There is a book which summarizes the fairly accurate calculation of the First Ionization Energy of ...
Stephen Elliott's user avatar
5 votes
0 answers
153 views

Combining two overlapping wavefunctions

Let's assume that we solved the many-body Schrödinger equation for two molecules and we can now write their wave functions as $$ |\Psi_1\rangle = O_1|\operatorname{vac}\rangle\,,\\ |\Psi_2\rangle = ...
mavzolej's user avatar
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5 votes
1 answer
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Atomic terms and perturbation theory

I have a question about the derivation of the possible atomic terms of an atom. Consider an atom with $N$ electrons in the central-field approximation, with hamiltonian $$ H_{0} = \sum_{i=1}^{N} \left[...
AlfredV's user avatar
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-3 votes
1 answer
131 views

Why are p orbitals most important for stability? [closed]

Is there nice way to see/show/derive why p orbitals are so important for stability? Or asked differently: Why are elements with filled p orbitals on the right side of the periodic table? Why aren't ...
user3700272's user avatar
1 vote
0 answers
109 views

Franck-Condon principle and shift of wavelength

I was revisiting my notes for spectroscopy, and I came across the Franck-Condon-principle. I understand it well, but want to clear some doubts regarding this. I know that the Franck-Condon-principle ...
Mäßige's user avatar
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0 answers
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Why SCF-MO methods fail when treating bond-breaking processes?

I'm currently studying the EVB(Empirical Valence Bond) approach. While reading on this article (https://pubs.acs.org/doi/10.1021/ja00224a011), the author mentioned about the usage of SCF-MO formalism ...
Arete's user avatar
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6 votes
2 answers
969 views

Jablonski diagram and absorption

I was reading about Jablonski diagrams and how they are structured. Bold lines would indicate ground electronic levels, and thin lines indicate the associated vibrational levels. Absorption only ...
Mäßige's user avatar
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2 votes
0 answers
80 views

Derivation of the conversion of Gaussian type orbitals (in cartesian coordinates) to Gaussian type orbitals (in polar coordinates)

While studying basis sets, I came across Gaussian type orbitals (GTOs), which are used as atomic basis sets. I reviewed the polar form of these orbitals, which are very similar to hydrogen atom ...
MeliodusSama's user avatar
2 votes
3 answers
449 views

Distance of Orbitals from Nucleus relation with Energy level and penetration power

I have studied that according to Aufbau rule the energy of subshells is dependent on the sum of $ n $ and $l$ values. This would imply that the energy of subshells in a shell varies as $$ ns \lt np \...
bm27's user avatar
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6 votes
0 answers
97 views

Obtaining transition density matrix

I'm trying to assemble a transition density matrix on quantum computer using one-body excitation $\widehat{E}$ operator on 2 active spatial orbitals, i.e. on 4 spin-orbitals. The problem is, I need to ...
Eenoku's user avatar
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2 votes
0 answers
62 views

Auxochrome groups and red shift

Wikipedia states that "An auxochrome is known as a compound that produces a batochromic shift, also known as a red shift because it increases the absorption wavelength, thus approaching infrared ...
Luckenberg's user avatar
4 votes
1 answer
84 views

Polyatomic molecule vibrational spectra - Molecular dipole expansion in Taylor series

To give some context: I am studying the molecular spectra in the context of an introductory course to atomic and molecular physics. My professor is using the transition rate expression from an initial ...
akkar's user avatar
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-2 votes
1 answer
80 views

Can't the wavelength of an electron increase or decrease to "fit" the wave perfectly in any radius?

I was reading about how de Broglie's electron-wave theory explained the quantisation of energy in a Bohr atom. What I understand is as follows: If the wave is to be arranged in the form of a circle ...
Arham Jain's user avatar
-4 votes
1 answer
209 views

What is the molecular orbital diagram of hydroxide anion? [closed]

Context I am a teacher, and, during a class, my student asked me to draw the molecular orbital (MO) diagram of the hydroxide anion ($\ce{HO-}$). First, I made the diagram on the left, and then, when ...
ananta's user avatar
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-3 votes
1 answer
127 views

How can we find a 3d sdf file if there is no in PubChem? [closed]

I'm looking for a 3d sdf file of BBr3. Though I cheked PubChem, there is no 3d file, but there is a 2d file. In that case, how can I get a 3d file, are there any other repositry on 3d file? or below ...
user250756's user avatar
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0 answers
124 views

Do all p orbitals really have the same energy?

If we solve the time-independent Schrödinger equation for any atom by considering only the electrostatic potential, an electron has the same probability of occupying the $p_{x}$ orbital as it does the ...
Volpina's user avatar
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2 votes
0 answers
99 views

Magnetic moment of an electron not parallel to its angular momentum?

For the total angular momentum of an electron $\vec{J} = \vec{L} + \vec{S}$, we're often shown a picture like this where I assume that the $\vec{L}$ and $\vec{S}$ cones are centred on the $J$ axis ...
Furrier Transform's user avatar
-1 votes
1 answer
105 views

Diagram of the electric field potential around water

Is there diagram of the electric field around a water molecule. I have seen some simplifications that treat hydrogen as a positive point source and oxygen as a negative point source. But I am looking ...
Q the Platypus's user avatar
-4 votes
1 answer
74 views

what happens to electron after beta minus decay [closed]

In the beta minus decay, electron is emitted from the nucleus. It depends on the previous nuclei(that was before beta decay) how much energy emitted electron will have. After this event, Internal ...
Giorgi Lagidze's user avatar
6 votes
0 answers
69 views

Are there examples of publications using DFT instead of HF as a coupled-cluster reference?

I have been searching for a while, and only managed to find an article by M. Saitow,[1] where CAM-B3LYP orbitals are used. I was wondering if this has been done elsewhere. It was recommended to me by ...
L. Hehn's user avatar
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-1 votes
1 answer
136 views

If atomic orbitals are orthogonal, how can one mix then in Molecular Orbital Theory?

If two molecular orbitals are orthogonal, their net overlap is 0. Which means that the mixture of them would result in no observable change in any of the orbitals if they occur. However, this ...
Andres Krasnikovas Perucelo's user avatar
2 votes
1 answer
129 views

Does the Hartree-Fock energy of a virtual orbital satisfy the virial theorem?

In calculating the ground state of atoms or molecules at the equilibrium geometry, the expectation values of the kinetic, $\langle T\rangle$, and potential, $\langle V\rangle$, energies relate to the ...
GeoArt's user avatar
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0 votes
0 answers
66 views

Can someone elaborate what it means when its said that electron shells do not exist in multi electron systems?

I'm an undergraduate student in chemistry. I'm trying to grapple with all the new stuff we're learning and making sense of it. Now I want to know if electron shells really "exist" in multi ...
Stu's user avatar
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2 votes
1 answer
89 views

What can visual observations of pi-bonding MOs explain about LCAO expansion coefficients?

For examples of CO and N2, what can their MOs tell us about their expansion coefficients? I've thought that in N2, its symmetric so the expansion coefficients would be equal from the pi-bonding MO due ...
Audrix's user avatar
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-2 votes
1 answer
71 views

Why is solubility affected by temperature? [closed]

Why when we raise temperature generally a bigger concentration of a soluble gets dissolved in a inorganic solvent?Is there a quantum mechanical reason why this is happening?
Volpina's user avatar
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