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How accurate are the most accurate calculations?

Exhibit 1: Ground state hyperfine splitting of the H atom: ...
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Why is my hydrogen energy not equal to -0.5 hartrees?

Yes, the exact orbital energy of the hydrogen atom is $-1/2\ E_h$. The problems in the calculation are as follows. First, you are running ROKS. ROKS has many definitions in the literature; PySCF ...
• 20k
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High precision helium energy

The 2006 variational calculation by Schwartz is lower (more accurate) than Nakashima & Nakatsuji's 2007 energy: ...
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How to determine which levels correspond to each other in LS coupling and jj-coupling?

In the jj-representation, each electron from $i$ to $N$ will have: $\vec{l}_i$ (orbital angular momentum), $\vec{s}_i$ (spin angular momentum), and $\vec{j}_i=\vec{l}_i + \vec{s}_i$ (total angular ...

Why is my hydrogen energy not equal to -0.5 hartrees?

The exact non-relativistic ground state electronic energy of a hydrogen-like atom, assuming that the nucleus is "clamped", point-sized, and with an infinitely large mass compared to the mass ...

How to get 192 of CeO2 atoms coordinates using Vesta?

The paper you link to identifies 4 Ce atoms and 8 O atoms per unit cell, which has the correct stoichiometry and seems a reasonable density for CeO2, so what is going wrong? The issue is that you have ...
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Acceleration of 8110823001207866000 m/s^2 by using Coulomb's law: did I do it right?

The other answer correctly pointed out that using $F=ma$ and the mass of the hydrogen atom does not give the exact $a$, and even if one uses the correct relativistic formulas and the correct mass, one ...
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For one atom, what is the correct point group?

When choosing the point group, a system with a single nucleus (e.g. a single atom) is considered to be spherically symmetric, so its point group is $K_h$ in Schoenflies notation, in which K stands for ...

Acceleration of 8110823001207866000 m/s^2 by using Coulomb's law: did I do it right?

"It rises the question, if Columb's law can be useful at such small/atomic scales?" Coulomb's law still plays a role in the Hamiltonian of an atom, but your discussion of "force" ...

Why can't DFT calculate the accurate electronic configuration of the Oxygen atom?

I am unfamiliar with this exact tutorial but this looks fine to me, you have 4 electrons in one spin and 2 in the other, giving a net 2 unpaired electrons. This is correct when you look at the ground ...
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Quantifying electronic overlap?

I recommend the use of Multiwfn package. This software is free with Windows/Linux versions. It uses the wave function calculated from other software. From the site: Briefly speaking, Multiwfn can ...
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Quantifying electronic overlap?

By the "metal cores", If you're referring to the overlapping of wave functions of electrons of metal ions separated by a distance, then you can in principle use quantum ESPRESSO to get some ...
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In which theoretical framework does the size of an atom depend on the temperature of the gas (Bose-Einstein condensates)

In calculations of the electronic energy/wavefunction, temperature typically is not taken in to account (besides cases of orbital occupation smearing, though this is used more as a computational trick ...
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In which irreducible representations shall I put the electrons in an F atom in PySCF?

If for oxygen you have: {'A1g': (2,2), 'E1ux': (1,0), 'E1uy': (1,0),'A1u': (1,1)} Then for fluorine I would simply put one more electron in either of ...

Finding the Configuration State Functions of Atoms

A configuration state function (CSF) is a symmetry-adapted linear combination of Slater determinants. Even for a small basis set, there can be trillions of CSFs. Those will surely not all be tabulated ...

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