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2
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1answer
85 views

Why do electrons not fully fill up all the orbitals sequentially?

Why do electrons not fully fill up all the orbitals sequentially? By this I mean: why don't the electrons fully take up the previous orbit first and then move onto the next orbit? Take calcium for ...
0
votes
2answers
41 views

How long does it take for an electron to be described in a quantum state?

Suppose we have a proton ($\ce{H^+}$). Suppose an electron comes to orbit the proton and starts to fall inwards. Suppose we know the exact position of the electron when it starts to orbit the proton. ...
1
vote
0answers
56 views

reconstruct the wave-function from one body reduced density matrix?

Given a many body wave-function for a Fermion system, we can calculate the one-body reduced density matrix straightforwardly. Now suppose we know the one-body reduced density matrix, is there a way to ...
0
votes
1answer
36 views

Is tight-binding modified by double bonds?

According to the tight-binding method, we can calculate the energy spectrum of a molecule, considering the wave-function as a linear combination of atomic wave functions centered at the atoms. For ...
1
vote
1answer
53 views

The Space Between Atoms And Sub-Atomic Particles And More [closed]

I was wondering what the space between atoms or electrons is called. Is it Vacuum ? And what is in there ? Is it really free or empty space ? And if so, how can nothing exist ? It is a bit of an odd ...
0
votes
1answer
45 views

calculating with quantum numbers and shape of nodal shells

I'm attending in a chemistry course now, and in the beginning we scratch the surface of the quantum physics, which have led me to some problems. Mostly I understand all what we get until now, but ...
1
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0answers
44 views

Change in energy eigenvalue of Schrödigner-Pauli equation

If I apply a uniform magnetic field to a paramagnetic material, I will re-orient the quantum spins of the electrons on the atoms to create a net magnetic dipole moment. When the re-orientation occurs ...
0
votes
0answers
18 views

Where can I find information on gas discharge tube mixes beyond the noble gases?

I have seen plenty of information on the noble gases, and oxygen and nitrogen. I haven't found much on other gases, or mixtures of gases. I don't really know where to look beyond google. I am in ...
2
votes
1answer
61 views

Atoms attraction [closed]

Do atoms attract to atoms of same element? And would atoms attract to another atom for forming ionic or covalent bond? I basically want to know what would an atom be attracted to? (Except for ...
1
vote
2answers
42 views

What happens to covalent bonds after the nuclear transmutation of an atom in a molecule?

What happens when we have a decaying atom in a molecule, which has covalent bonds with other atoms? I assume some of the bonds will cease to exists, but I did not manage to find any rule about which ...
1
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0answers
20 views

What happens for cyclopentadien radical? [closed]

for cyclopentadien radical secular determinand find energy values? delocalization energy for cation radical and anion? what is solution? I cannot solve please help
5
votes
1answer
295 views

Are orbitals observable physical quantities in a many-electron setting?

Orbitals, both in their atomic and molecular incarnations, are immensely useful tools for analysing and understanding the electronic structure of atoms and molecules, and they provide the basis for a ...
2
votes
1answer
43 views

Problem using spin-restricted form of the second-quantized nonrelativistic Hamiltonian

I have a problem that confuses me a lot. The two-electron part of the electronic nonrelativistic Hamiltonian can be written \begin{equation} \frac{1}{2}\sum_{pqrs} (pq|rs) [a^\dagger_{p\alpha}a^\...
1
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0answers
48 views

Effect of doping in Superconductor

Doping an element (for example element substitution) could be lower down the critical temperature of superconductor, but i don't know the mechanism behind this, is it because more bosons need to ...
5
votes
2answers
526 views

Mutual or same set of eigenfunctions if two operators commute

If two operators commute, do they have "a mutual set of eigenfunctions", or "the same set of eigenfunctions"? My quantum chemistry book uses these as if they are interchangeable, but they do not seem ...
1
vote
1answer
34 views

Spin-$\frac{1}{2}$ particles in chemistry

Electrons and protons are spin-$\frac{1}{2}$ particles, so under a rotation by 360$^\circ$, their wavefunction changes by a sign. They are also commonly found alone in chemical reactions, especially ...
2
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0answers
13 views

How does one calculate chemical shift in a gauge independent manner?

The literature on ab initio calculations of chemical shift in NMR experiments usually provide Lamb's and Ramsey's formulae as the solution. Yet the expressions explicitly depend on vector potential ...
0
votes
3answers
456 views

Does a single photon's energy depend on frequency? (photoelectric effect)

Essentially this question boils down to "why does the energy of light depend on frequency?". The analogy my textbook (pg. 272 principles of chemistry A molecular Approach 3rd edition by Nivaldo J. ...
0
votes
1answer
52 views

Expectation value of the hydrogen atom:$ sp^2$ hybridisation

For $n=2$, \begin{equation} \psi_0=R_{20}(r)/4\pi \quad \psi_1=R_{21}(r)\sqrt{3/4\pi} x/r \quad \psi_2=R_{21}(r)\sqrt{3/4\pi} y/r \quad \psi_3=R_{21}(r)\sqrt{3/4\pi} z/r \end{equation} When I compute ...
2
votes
2answers
51 views

When dihydrogen is formed, are photons being emitted?

When a hydrogen in an excited state transits back to the ground state, a photon (or series of photons) is emitted in accordance with the selection rules. When two free hydrogen atoms in the ground ...
1
vote
3answers
253 views

How could an s and p subshell occur together in an atom?

s: Subshell of an atom has spherical shape. p: Subshell is a dumb-bell shaped with a node at center of the atom. If we put two shells together they would intersect in an atom. In such a model, ...
0
votes
1answer
79 views
2
votes
2answers
207 views

Calculating the radius and potential energy of an atom?

Is there a general equation that gives the potential energy of any element at each energy level? I know that there is an equation for the potential energy of a hydrogen atom at each energy level but ...
0
votes
0answers
25 views

Software for BEC dynamics in optical lattice

I am looking for a quantum chemistry software that deals with Bose-Einstein condensate in optical lattices (1D, 2D, 3D). I am interested in full many-body Schrodinger equation (two-body interactions - ...
1
vote
2answers
74 views

Trying to understand lowest configurations of carbon

My study group is debating about which are the three lowest configurations of carbon. I've been arguing that the electron has to jump to the 3s level for the configuration to be different. Others have ...
12
votes
2answers
310 views

Why does the conjugated $\pi$ bond not violate the Pauli Exclusion Principle?

Let's look at the molecule 1,3 butadiene: $CH_2=CH-CH=CH_2$ and number the carbon atoms 1 to 4 from left to right. The bonds between 1 and 2 and between 3 and 4 are double bonds: each ...
1
vote
1answer
159 views

When i tear a paper, can i accidentally create nuclear fission?

I know it's a stupid question... but when I tear a paper i may coincidentally split it and create nuclear fission. When i tried experimenting, by tearing the paper for HELLKNOWS how many times, I ...
2
votes
0answers
89 views

Why is the activation energy of combustion so large compared with regular bonding?

I wanted to know why combustion requires an activation energy and I found this article (see this too). It says that molecular oxygen ground state is a triplet state (according to Hund's rules), and ...
0
votes
1answer
68 views

One-electron reduced density matrix: Argument for positive semidefiniteness

I cannot follow an argument for positive-semidefiniteness of the one-electron density matrix given in "Molecular Electronic-Structure Theory" by Helgaker/Jorgensen/Olsen. First some definitions: $F(M)$...
14
votes
2answers
980 views

Is there experimental verification of the s, p, d, f orbital shapes?

Have there been any experiments performed (or proposed) to prove that the shapes of the s,p,d,f orbitals correspond to our spatial reality as opposed to just being a figment of the mathematics that ...
1
vote
1answer
46 views

Are differences between elements besides the number of valence electrons negligible in forming matter and giving certain properties?

We were talking about life complexity, I don't know almost anything about physics, he told me that differences between elements beside the number of valence electrons are negligible and elements with ...
2
votes
1answer
362 views

What is the difference between real orbital & complex orbital?

While reading Atomic orbitals, I came before these two terms. The 'real orbital' is given here: Real orbitals An atom that is embedded in a crystalline solid feels multiple preferred axes, ...
0
votes
1answer
64 views

Software to calculate electron binding energy of molecules?

I need to calculate the binding energies for the various electrons in a few different molecules (to determine an appropriate wavelength to selectively ionize them). Are there any software packages to ...
3
votes
1answer
106 views

Finding Electronic Energy Levels by Representation Theory

Let $$u=\left( \begin{array}{cccc} c_1&c_2&c_3&c_4 \end{array} \right)^T$$ for $$\psi = c_1\psi_1 + c_2\psi_2 + c_3\psi_3+ c_4\psi_4$$ We assume that $\left<\psi_i|\psi_j\right> = \...
0
votes
2answers
789 views

Correlation energy - is it the difference between the Hartree-Fock energy and exact energy, or Hartree-Fock PE and exact PE?

For some reason I can't find anything stating it either way explicitly. What I'm talking about is this. Is this difference referring to potential energies or just energies in general? I assume it's ...
1
vote
0answers
53 views

Why don't wavefunctions for electrons in neighbouring molecules overlap?

I've come across this picture of two linked molecules. The intramolecular distances look similar to the intermolecular distances and it seems like that will be the case however you draw it because of ...
1
vote
2answers
120 views

Atomic orbitals

I just studied atomic orbitals in a theoretical QM class, and I'm left with several questions, that are probably more questions in quantum chemistry: Many orbitals seem to have a preferred axis - ...
2
votes
0answers
9 views

What would be the Slater's determinant of an excited state? [duplicate]

Setup Introducing this spinorbital notation: \begin{align} \Psi_1=\chi_{(r1)}\alpha_{(\omega1)} &= 1 \\ \Psi_1=\chi_{(r1)}\beta_{(\omega1)} &= \bar{1} \end{align} and the Slater's ...
3
votes
0answers
90 views

Geometric measure of entanglement for fermions or bosons?

For a system consisting of multiple components, say, a spin chain consisting of $N\geq 3 $ spins, people sometimes use the so-called geometric measure of entanglement. It is related to the inner ...
1
vote
1answer
112 views

Does O$^{2-}$ really exist?

In chemistry it is common sense that we have O$^{2-}$. But from a physical point of view, does O$^{2-}$ really exist as a negative ion? I mean, as an isolated ion. It is not apparent that a neutral ...
1
vote
2answers
143 views

How to use Hartree-Fock for helium?

I am thinking of using Hartree-Fock approximation to calculate the ground state energy of helium. The ground state wave function must have a symmetric orbital wave function. But in HF we need a Slater ...
2
votes
6answers
1k views

Rutherford's gold foil experiment: can alphas be deflected by electrons vs. nucleus?

In this experiment, is it possible that some of the alpha particles are deflected by the electrons? Gold, after all, usually also has ~79 of them in each atom. Since the alpha particles want ...
0
votes
1answer
479 views

Kinetic energy (KE) in atomic orbital

Within an atomic orbital, electrons must obviously have relative differences between points in space due to potential gradient. But there is kinetic energy as well. If we choose a particular point as ...
1
vote
2answers
49 views

Bond Formation during reaction

My Chemistry textbook says that on approaching each other, atomic orbitals of atoms interact. This interaction, it says, can be additive and subtractive, and lead to formation of bonding and anti-...
3
votes
0answers
96 views

Quantum Mechanical Thinking

I've just been wondering about how atoms and molecules can be quantum mechanically thought about, and I have a question. It is often said that intermolecular bonding is purely "electrostatic". I hope ...
1
vote
1answer
95 views

How to find bond length from potential?

A bonding potential like the Morse potential or a Lennard-Jones potential is characterized by a distance at which the potential is minimal, referred to as e.g. 'equilibrium bond distance'. Is this ...
0
votes
1answer
43 views

Applying the time evolution operator as a form of molecular dynamics

I had a kind of weird idea. In molecular dynamics, long timescale simulations (like protein folding) are a really hard problem because you can't "skip steps" of the simulation without huge ...
2
votes
2answers
114 views

Wavefunction of isomers

In quantum chemistry, the wavefunction for a molecule can be viewed as the output of a function $\xi(m, n_1,..., n_k)$ with $m, n_i \in \mathbb{Z}^+$ that returns a $|\psi\rangle$ that satisfies a $H|...
2
votes
4answers
480 views

Two soft questions about spin and the particle nature of electrons

How can we define spin as the spin of an electron around it's own axis if an electron is described by a probability cloud of finding an electron in a point in space? How does that probability cloud ...
1
vote
1answer
262 views

How many wavefunctions are in a minimal basis set for benzene?

I am reading Modern Quantum Chemistry by Szabo and Ostlund and on page 62 he says "A minimal basis set for benzene consists of 72 spin orbitals." I tried to understand this number but failed. ...