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
0
votes
0answers
130 views

What is meaning of LAV2P basis set?

I am working on energy optimization of molecular structure using DFT with Schrödinger software and I found that job is running on LAV2P basis set. I want to know what is the meaning of this basis set ...
0
votes
2answers
349 views

What does Brightness/ intensity of spectral lines depend on?

My book states that it depends upon "The number of photons of same frequency or wavelength ABSORBED or EMITTED" From what I understood, if many hydrogen atoms within the discharge tube EMIT the same ...
0
votes
0answers
39 views

Ionization energy and charge localization: π-bonds/systems and ionization energy

Page 35 of my textbook, Mass Spectrometry by Jürgen H. Gross, says the following in a section on ionization energy (IE) and charge localization: Molecules with π-bonds have lower IEs than those ...
0
votes
0answers
98 views

Does the radius of the atom change when an electron is excited?

The radius of the atom increases when the electron in a hydrogen atom undergoes a transition from the 1s-orbital to a 2p-orbital. How is this possible? Why does exciting an electron to a higher ...
0
votes
0answers
53 views

Getting radial Kohn-Sham orbital from the output of an electronic structure code using gaussian basis sets

As we know that in solving the Schrodinger equation (Kohn-Sham equation), we expand the wavefunction in terms of some basis sets and them optimize the energy (the expectation value of Hamiltonian) by ...
0
votes
0answers
80 views

What is the significance of antinode at r=0 in the plot of radial wave functions of s-orbitals?

Why should there be an antinode at r=0? I can comprehend the presence of node at r=0 for p,d,f orbitals; but I don't understand that of s-orbital. Is there any intuitive approach?
0
votes
0answers
46 views

Is it possible to calculate electrostatic interactions using QM methods?

I'm trying to calculate an accurate electrostatic repulsion (and possibly attraction) energy term for various small molecules, using Quantum Mechanics (QM) methods. These may include molecules such as ...
0
votes
1answer
32 views

Potential energy curve for dissociation of cation of carbon dioxide

Can anyone suggest me some literature where I can find the potential energy curve or the electronic states for singly ionized $\ce{CO2}$ ($\ce{CO2+}$) dissociating into singly charged oxygen ($\ce{O+}$...
0
votes
0answers
45 views

Photoelectric effect — Expected observations for waves

I understand why treating light as particle-like photon packets leads to the observed results. I seek to understand why one would expect different results if light were treated as a wave (and thus ...
0
votes
1answer
66 views

Can the oxidation of hydrogen peroxide be reversed? [closed]

Hydrogen peroxide is said to be unstable, for it undergoes auto-oxidation on standing/heating: $$\ce{2H_2O_2 -> 2H_2O + O_2}$$ where $\Delta S=\pu{70.5 J {mol}^{-1}K^{-1}}$ and $\Delta H^{\Theta} ...
0
votes
0answers
64 views

Significance of this unusual matrix element

Recently, I was solving some questions on Rigid Rotor. I found this question very amusing. Evaluate the integral i) <$Y_{l,m+2}$ | $L_{x}^{2}$ | $Y_{l,m}$ > I evaluated it, found that the value ...
0
votes
0answers
179 views

Why do we neglect the zero point energy in statistical mechanics?

Quantisation associated with translational modes can be modelled like a particle in a box (PiB). $$E_n = \frac{n^2h^2}{8mL^2} \qquad n \in \mathbb{Z} \, | \, n \ge 1$$ By the equation above, the ...
0
votes
0answers
22 views

Scan type of DFT calculations adding Freq=Raman keyword [duplicate]

I´m doing a scan calculation by adding Freq=Raman keyword. My objective is to obtain the Raman spectrum of each conformation in my compound. However, when i write the Freq=Raman Keyword, only the ...
0
votes
0answers
242 views

Is OH + CO → CO2 + H an elementary reaction?

Is $$\rm OH + CO \longrightarrow CO_2 + H$$ an elementary reaction? How could I tell? I could break the reaction into $$\rm OH\ (+ M) \longrightarrow O + H\ (+ M)$$ $$\rm CO + O \longrightarrow ...
0
votes
0answers
797 views

Why does q/m ratio(specific charge) depend on nature of gas in anode ray experiment?

I can't understand why $q/m$ ratio changes in anode ray experiment (discharge tube experiment) (which was carried out by Goldstein) with change in nature of gas? Since $q=1.6\times10^{-19}\ \mathrm C$...
0
votes
0answers
59 views

Schrödinger's equation [duplicate]

Schrodinger's equation has been successfully solved in one-electronic systems, such as the ionic molecular hydrogen $\ce{H2+}$. What is the exact reason that this equation can not be applied for ...
0
votes
0answers
20 views

Filling up of electrons [duplicate]

Is it necessary that filling up orbitals start from spin-up orientation only? And also, is it mandatory to fill the electrons with one kind of spin or they can be filled with spin up and spin down(as ...
0
votes
0answers
36 views

Using knowledge of radial distribution functions, how is it possible to explain the different electron configurations of V3+ and Calcium [duplicate]

I recognize that the 3d orbital decreases in energy to lower than the 4s once it becomes occupied (even if I don't completely understand why?!). However, how is the difference in electron ...
0
votes
1answer
1k views

If the electron of a hydrogen atom transitions from energy level n=5 to n=3, which level corresponds to n1 and which level corresponds to n2 [duplicate]

which level corresponds to n1 and which level corresponds to n2 in the Rydberg equation?
-1
votes
3answers
68 views

$\psi$ Represents amplitude of electron wave and $\psi^2$ represents electron density in a given space. How?

The $\psi$ represents amplitude of electron wave. So it's dimension should be $\left[L\right] $. But $\psi^2$ represents density of electrons in a given space. So it's dimension should be $\left[ML^{-...
-1
votes
1answer
3k views

Why the second ionization energy of helium is greater than the first? [closed]

maybe because the first electron has a lower energy. Why does this happen?
-1
votes
1answer
48 views

Can carbon have electrons in a 5d orbital? [closed]

(a) Sketch the radial probability distribution for a 5d orbital in a carbon atom. You should label the axes, but do not need to include numbers. Use arrows to indicate the radial nodes. (b) Label the ...
-1
votes
1answer
165 views

Quantum Chemistry, quantum physics [closed]

In both classical and quantum mechanics knowledge of the present state of an isolated system allows it's future state to be calculated. If yes then why if not then why ?
-1
votes
2answers
257 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 ...
-1
votes
1answer
190 views

Band gap of Transition Metal Dichalcogenides

What phenomena is responsible for the shift of the nature of the band gap of transition metal dichalcogenides from being indirect band gaps to direct band gap material once it is slimmed down from ...
-1
votes
1answer
545 views

Potential energy of electron in excited hydrogen atom

The angular momentum of electron in an excited H atom is $\frac{h}{\pi}$. The potential energy (PE) of electron is? Let $\frac{h}{\pi}=\frac{nh}{2\pi}$, therefore $n=2$. So, $$E=\frac{-13.6}{4}=\pu{-...
-1
votes
1answer
444 views

Explain!“An orbital of smaller size means there is more chance of finding an electron near the nucleus” [closed]

how can orbital of smaller size increase the probability of finding the electron near the nucleus Please explain in simple language.
-1
votes
1answer
44 views

How to find the number of valence electrons with the help pf quantum numbers? [closed]

I'm bit confused on how to find the number of valence electrons. For example, Boron ($\ce{B) has the electronic configuration as: $\mathrm{1s^2 2s^2 2p^1}$. So what would be its number of valence ...
-1
votes
1answer
32 views

Absorbance maxima of polyenes [closed]

Can anyone tell me how to approach this question from USNCO 2013?
-1
votes
1answer
34 views

What is the velocity of de Broglie wave?

Here is my calculation: note: $ν$ – frequency, $V$ – velocity of wave, $v'$– velocity of object. $$ \begin{align} λ &= h/mv' \tag{1}\\ mc^2/h &= ν \tag{2}\\ λν &= V \quad \text{(wave ...
-1
votes
1answer
49 views

Quantum Chemistry [closed]

How to find the degeneracy of a given state in quantum mechanics? What is the formula?
-1
votes
1answer
51 views

How is it that the Inner Periodic Table Sections (have 15 elements each) versus their f-block (with only 14 element’s electrons each)? [closed]

Given: 1. the “Lanthanide and Actinide” Inner Periodic Table Sections (each have 15 elements) versus the f-block Orbitals (which only have a capacity for 14 out of the 15 element’s electrons each) - ...
-1
votes
1answer
124 views

Schrödinger wave function for 3s orbital of hydrogen atom [closed]

I am unable to understand what these terms in the wave function represent and how to solve it. For 3s orbital of hydrogen atom, the normalised wave function is $$Ψ_\mathrm{3s} = \frac{1}{81\sqrt{3π}}\...
-1
votes
1answer
53 views

Chemical reaction energy barrier width [closed]

Well chemistry before the discovery of quantum world was saying:"In order for a chemical reaction to happen , reactants must have enough energy to be converted into products."I was wondering now that ...
-1
votes
1answer
165 views

How to give different Basis set to different atoms in molecules using GAMESS-US [closed]

I am new to GAMESS-US, I am trying to do UHF for DyC10H10 while giving different basis set to Dy, C, H to reduce the computational cast. Until I tried with following input using manual. OUTPUT *** ...
-1
votes
1answer
91 views

What happens if the electron in the lowest energy level of an atom loses its energy?

What happens if the electron in the lowest energy level of an atom loses its energy? Excited states spontaneously give of energy and transition to a lower energy state. Why can't an electron in the ...
-1
votes
1answer
178 views

What is the difference between carbon in an excited state and with sp³ hybridization?

What is the difference between the carbon in the excited state, $\ce{[(1s)^2] (2s)^1 (2p)^3}$, and $\pu{sp^3}$ hybridization?
-1
votes
1answer
148 views

Is there a fixed corresponding orbital for every specific magnetic quantum number? [duplicate]

Does each value of $m$ have a fixed orbital (given the value of $l$ as well as $n$)? For example, if I know that $n = 2$, $l = 1$, and $m = -1$, which orbital ($\ce{p_x}$, $\ce{p_y}$ or $\ce{p_z}$) ...
-1
votes
1answer
32 views

how electron can go towards nucleus and then go far apart from it as in p orbital?see discription

In p orbital shape is dumbbell shaped which means electron go in the shape of dumbbell means first towards nucleus then go away from it. How can be this possible because first electron is attracted ...
-1
votes
1answer
89 views

From a Quantum Chemistry Point of View how can I break Bonds without Heating?

Is it possible to dissolve/break bonds using strong alternating magnetic fields at high frequency? (Perhaps from tesla coils?) Could you use resonance to cause the bond to weaken over time? If so how ...
-1
votes
0answers
83 views

Two questions about rotation of a single atom

1. Some sources state that physical rotation of monoatomic molecules or rotation about the internuclear axis of a linear polyatomic molecule are non-physical (because of symmetry) and are therefore ...
-1
votes
1answer
39 views

Help understanding the equation for Spin Energy in Zero Field

I’m working with a system that experiences spin frustration and for me this is the first time dealing with such a phenomenon. To grasp the concept, I’ve decided to go to the basics and read the ...
-1
votes
2answers
60 views

Why is the first affinity energy negative?

So, I've found a number of somewhat obscure responses to this question but I'm looking for something concrete: Why is the first affinity energy negative for most elements? I appreciate that this is ...
-1
votes
1answer
128 views

if the shared electrons in covalent bond revolves around their nucleus, how they hold the two molecules together? [duplicate]

Covalent bonds are formed by sharing electrons. The pictures depicting this bond make it seem like that the shared electrons stay in a fixed/limited place. What happens in reality? If they rotate ...
-1
votes
1answer
519 views

what is meant by stability and potential energy of molecules in cases of formation of bonds?

molecules form chemical bonds in order to gain stability. it is said that forming bonds leads to lower potential energy of molecules and makes them stable. what does stability mean? how formation of ...
-2
votes
2answers
503 views

What is the magnetic quantum number -1 vs +1?

In my book it states the magnetic quantum number “$m_\ell$" is the spatial orientation of the orbital with respect to a standard set of coordinates. I get what $n$ and $\ell$ is, but what does it mean ...
-2
votes
1answer
42 views

What is the physical significance of the fact that spin operators do not commute? [closed]

So we looked at the Stern-Gerlach experiment and I understand the basic principle; when a stream of silver atoms is passed through an inhomogeneous magnetic field, and the Ag atoms are deflected ...
-2
votes
1answer
156 views

Creating Pi Molecular Orbitals from P Atomic Orbitals

As shown in the image, we have two free p orbitals in ethene but we need two p orbitals each for the bonding and anti-bonding orbital. That is a total of four. What is the concept behind this?
-2
votes
3answers
57 views

Particle-wave duality for atoms [closed]

Hmm Hello . I was wondering if we could apply the particle-wave duality of a subatomic particle for an entire atom.I know that atom is better described as space but could we apply the de Broglie ...
-2
votes
1answer
270 views

why molecules gain energy when heated?

molecules in solid or liquid or gas gain kinetic energy when heated. why is it like this? I request explanation in details please