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, ...).

Filter by
Sorted by
Tagged with
1
vote
0answers
46 views

quantum capacitance of supercapacitor electrodes, high or low needed?

quantum capacitance of supercapacitor electrodes should be low or high? to achieve high specific capacitance. The quantum capacitance forms among the layers of low DOS materials when used as an ...
1
vote
0answers
120 views

How fast do electron's quantum spin flip?

In a recent lecture it was taught that carbenes with their electrons in a triplet configuration do not undergo concerted reactions as one of the electrons must first undergo a spin flip; on what ...
1
vote
0answers
59 views

Computational chemistry: is k a quantum number

I am trying to use the natural band offset method to calculate band offsets of junctions. In order to do so, I need to find the core electron eigenstates. I tried using FP-LAPW software Elk. But in ...
1
vote
0answers
488 views

How does symmetry of half filled and fully filled orbitals lead to stability

I googled a lot about why symmetry of half filled and fully filled orbitals decreases their energy but every time it is repeated that symmetry leads to stability. So the question is why symmetry leads ...
1
vote
0answers
245 views

Particle in a box models for polyenes and quantum dots [duplicate]

I'm kind of new to physical chemistry and trying to understand how, if at all, the correspondence principle (in the limit of large quantum numbers, quantum mechanics reproduces classical behavior of a ...
1
vote
0answers
352 views

Radial nodes in molecular orbitals

Do radial nodes exist in molecular orbitals? Radial nodes exist in atomic orbitals and the number of radial nodes for an atomic orbital can be determined by the general formula $n-l-1$ where $n$ is ...
1
vote
0answers
45 views

determine at which v and J the rotational and vibrational energy differences are equal

I was presented with this question and I started working on it but I ran into a problem. We've got $\Delta E_{rot} = 2B_e(J+1) $ and $\Delta E_{vib} = \hbar \omega$ We get to the point that we've ...
1
vote
0answers
655 views

Gaussian: Warning - assumption of classical behavior for rotation may cause significant error

I am playing around with a prostaglandin molecule (23 heavy atoms) in Gaussian09. My goal is to calculate the vertical ionization potential and electron affinity for the molecule. I already managed to ...
1
vote
0answers
37 views

Which MO approximation best fits with lab results and observation? [duplicate]

I understand that there are many different methods that can be used to approximate the set of MOs for an arbitrary molecule, as the actual quantum mechanical description is taxing to calculate. I just ...
1
vote
0answers
49 views

phase differences between conical intersections and light-induced conical intersections?

I've read recently about light-induced conical intersections, a phenomenon where conical intersections can be artificially introduced to molecules, and that this can be observed even in diatomic ...
1
vote
0answers
119 views

Calculating Optical Absorption Spectra using Ab Initio Computations

My main question is, How does one compute the optical absorption spectra of a molecule by using say, Configuration Interaction energy and associated transition dipole moments. I am trying to use an ...
1
vote
0answers
127 views

How do i make an molecular orbital diagram step by step?

My professor explained me, but i'm still unable to do a correct molecular orbital, for a diatomic molecule
1
vote
0answers
56 views

Why do ionisations from non-bonding orbitals result in little/no vibrational structure in a photoelectron spectrum?

I understand that ionisations from bonding and antibonding orbitals create vibrational structure from the Franck-Condon principle, resulting in a greater overlap integral between different vibrational ...
1
vote
0answers
174 views

Conical intersection using GAMESS

I would like to know how to locate conical intersection using a GAMESS calculation. I really appreciate an example alone with this since I am a novice I do not have a clear idea among bunch of ...
1
vote
0answers
40 views

Identifying the dependence of various time-independent wavefunctions

I'm tasked with finding the variables that each of the following wavefunctions depends on: (1) a free particle in 2 space (2) a free particle in 3 space (3) a hydrogen atom (4) a lithium atom. for ...
1
vote
0answers
63 views

Excitation Source for visible emitting Quantum dots

I read that the best excitation source for visible emitting quantum dots is UV light of wavelength $\mathrm{360~nm}$ to $\mathrm{380~nm}$. But why should the excitation source have lower frequency ...
1
vote
0answers
180 views

Use of statistics in this field

I am currently pursuing a statistics course and I an interested in knowing how can statistics help this field in future. (I am interested because I love chemistry very much) Specifically, are there ...
1
vote
0answers
47 views

Sulfur atomic absorption

Would the atomic absorption from FAA for Sulfur be from 3s2 -> 3p4 or 3p4 -> 4s0? I think according to the electronic partition function, there would be zero electrons in the 4s0 state at the ...
1
vote
0answers
83 views

Help solve this specific linear schrodinger equation, please

$$\left[-\frac{1}{2}\nabla^2 - \frac{2}{r} + C\right]\phi(r) = E\phi(r)$$ where $C$ is a known function. I am just looking for some help on the strategy to solve explicitly for $\phi(r)$. One thing ...
1
vote
0answers
327 views

How do I calculate principal quantum numbers of the Lyman series

How do I calculate principal quantum numbers of the Lyman series? I've been given that the lowest line is 121.6nm and the 5th line is 93.8nm The formula of the wavenumber is v=-R(1/n2^2 - 1/n1^2) ...
1
vote
0answers
373 views

QMOT | Orbital mixing in methyl

The following picture is from E. V. Anslyn Physical Organic Chemistry and shows constructing of MO of methyl using QMOT. MOs $\textbf{E'}$ and $\textbf{D'}$ are formed by mixing $\textbf{D}$ and $\...
1
vote
0answers
93 views

Experimental Validation of Schrodinger's Electron Cloud theory

I am currently doing a report for school on the electron cloud atomic structure theory. One of the major points on my report is the experiments performed by the scientists (Schrodinger and Heisenberg) ...
1
vote
1answer
1k views

Physical Meaning of the Difference between MO and VB Wave Function of H2?

What would be the physical meaning of the difference between the MO wave function and VB wave function of $\ce{H2}$?
0
votes
2answers
19k views

What happens when we heat an atom?

Question is simple.. If we take an atom of any element and then supply heat energy to it then what will happen? What I thought is that in the beginning, energy (quanta; due to excitement of electron ...
0
votes
2answers
64k views

How to find the number of valence electrons?

I need to understand the following: Considering an element Sulfur - S which has 16 electrons. How do we calculate the number of valence electrons of S? Please correct me if I am wrong:2+2+6+2+4=16. ...
0
votes
1answer
1k views

How to calculate probability of finding an electron at a point?

In school i learned how to calculate probability of finding electrons in some volume but how can we calculate the probability of finding a electron at a particular point. Point here ...
0
votes
1answer
894 views

H2 Triplet State

How does $\ce{H2}$ triplet state exist if there are electrons in both bonding and antibonding ($1\sigma$ and $1\sigma^*$) orbitals? Or am I being taught the hypothetical triplet states of the ...
0
votes
1answer
136 views

Electron vs electron density

I recently read somewhere that electrons do not exist. it's just the electron density. Is it true that there are no electrons (particles) but only in the form of electron density? And does this ...
0
votes
2answers
197 views

Why do 1s and 2s orbitals intersect? [closed]

So I was going through the Schrödinger wave equation to determine the shapes of orbitals. We know that an orbital is nothing more than a region where probability of finding an electron is maximum. ...
0
votes
1answer
99 views

Is the pz orbital wave function three- or four-dimensional?

The wave function of the $2\mathrm{p}_z$ orbital is $$Ψ = \frac{1}{4\sqrt{2π}}\left(\frac Z a\right)^{5/2} r \mathrm e^{-Zr/a}\cos θ.$$ I'm confused if this function will be a three-dimensional ...
0
votes
2answers
102 views

Spin Operator algebra

I am trying to teach myself some QM. In Christopher J. Cramers textbook Essentials of Computational Chemistry: theory and models, in Appendix C, he goes over Spin algebra. I am unable to calculate ...
0
votes
2answers
88 views

Hamiltonian 2nd positional derivative analogous to acceleration?

In Quantum Mechanics, we learn that the Hamiltonian operator for an electron confined to a 1-D space is: We learn in QM that many operators have analogous interpretations familiar to us from ...
0
votes
1answer
989 views

Degenerate orbitals in the Hydrogen atom

I came across the following link: Which orbitals of the hydrogen atom are degenerate for $n=3$ And all the answers said that for the hydrogen atom, the energy of an orbital depends only on n. Is ...
0
votes
1answer
94 views

when do we indicate the “+ or -” sign in uncertainty [closed]

how can we know when to indicate "+ or -" sign in uncertainty calculations because I noticed some problems has been solved by this sign and some has not.
0
votes
1answer
85 views

What does Pauli’s exclusion principle mean in atomic or fundamental way? [closed]

It means is that no electron can have same n , l and $m_l$ but can have two different spin quantum number. I want to know why is this rule valid?Means there must be some other things happening also ...
0
votes
1answer
106 views

How can an electron being a wave have such property as spin?

Here's what I know about electrons. Electrons have wave-like properties and the number of wavelengths in the $n^\text{th}$ shell is equal to $n(\lambda).$ Also, I read in my book that they have ...
0
votes
1answer
162 views

Quantitative MO theory- how is the overlap integral and the weighting coefficients of the molecular orbital actually evaluated?

Title. In my inorganic chemistry course, we learn about SALCs and qualitative MO treatment, with only a fleeting reference to the S integral and actual molecular wave functions (only hydrogen, $\ce{H2}...
0
votes
1answer
205 views

Relationship between the first and the second quantum number

Does the secondary quantum number tell how many subshells a specific principal quantum number shell has? E.g., if the principal quantum number is $n$, there are ($n-1$) subshells.
0
votes
1answer
60 views

why we can use the equipartition theorem for translational motion of molecules at room temperature and above because quantization is unimportant

From the book Chemical Principles The Quest for Insight, 5th Edition by Peter Atkins, Loretta Jones The equipartition theorem is a result from classical mechanics; so we can use it for translational ...
0
votes
1answer
85 views

Classically permitted position values in a quantum harmonic oscillator [closed]

In a quantum harmonic oscillator that is in the state with quantum number $n$, what range of the position $x$ is allowed classically? Does it have something to do with Bohr's correspondence principle?...
0
votes
1answer
87 views

What is the form of the Hamiltonian for solids?

For atoms, and even molecules, I can understand how the Hamiltonian would be constructed, but what of solids (as in, for electronic structure calculations)? Thank you for any help.
0
votes
1answer
69 views

antisymmetric wavefunction [closed]

Why can't we choose any other antisymmetric function instead of a Slater determinant for a multi-electron system? Why do we choose our wavefunction for a multi-electron atom as a product of single-...
0
votes
2answers
289 views

Is this what an orbital means?

In this picture, there is a $1s$ and a $2s$ orbital. Are the orbitals only the dark gray circles ? Or are the light gray circles (which are surrounding the dark gray ones on both sides) also included ...
0
votes
1answer
1k views

Angular Momentum Of S-subshell of an atom?

The angular momentum of every S-subshell of an atom is 0 by Azimuthal Quantum No. Relation. But if angular momentum of S-subshell is zero. Then by, Angular Momentum =Mass×Velocity×Radius; Radius of S-...
0
votes
1answer
2k views

Which is the bigger ion, F- or O-?

Well, according to the proton-electron ratio $\ce{O-}$ should be bigger than $\ce{F-}$ What about the charge/electron density in $\ce{F}$? Will it not affect the size of the atom of $\ce{F-}$?
0
votes
2answers
103 views

Why is the radial distribution at the nucleus 0 but not the radial wave function?

The modulus squared of the radial wave function gives the probability of finding an electron in an infinitesimal volume dv. On the other hand, the radial distribution gives the probability of finding ...
0
votes
2answers
1k views

Binding energy vs. ionization energy [closed]

I am studying binding energy in the context of photoelectric spectroscopy, and I came across a graph of relative numbers of electrons vs binding energy (in units of megajoules per mole). The element ...
0
votes
1answer
83 views

Quantum mechanics electron probability [closed]

Schrödinger's equation yields us the solutions of 90% probability of presence of electrons in orbitals. Hence, the electrons in theory should be able to exist elsewhere in space as well. In that case, ...
0
votes
1answer
63 views

Expression of the potential in the hydrogen atom while solving radial part of the wave function

I was reading about the derivation of wavefunction of Hydrogen atom from Atkins book. After the separation of variables and writing the wave function, $\psi_{(r,\theta,\phi)}=R_{(r)}Y_{(\theta,\phi)}$...
0
votes
1answer
67 views

Do quantum particles have mass? [closed]

Quantum particles are never objects but are always waves. But do they have mass or can they carry mass?

1
21 22
23
24 25
27