15 votes

On the nature of zero-point energy (ZPE)

In the Born-Oppenheimer approximation nuclei are assumed to behave as classical point-like particles. However, in reality the wave-particle duality also applies to them, and so the Schrödinger ...
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14 votes

Converting adsorption binding energy to absolute temperature

If I want to break a Li$_2$ molecule (i.e. remove atom A from atom B), one way to do it is by shining a laser on it such that the frequency ($\nu$) or energy ($h\nu$) corresponds to the difference ...
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8 votes

Converting adsorption binding energy to absolute temperature

A more approximate but sometimes easier approach than the one of Nike Dattani might be to calculate an artificial reaction coordinate of separating the two systems. This can be done manually or by ...
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7 votes

How to calculate temperature dependent phonon band structure in VASP

There are two main contributions that can be included in the DFT context when calculating phonons at finite temperature: Thermal expansion. As temperature increases, the volume of materials changes (...
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  • 10.4k
7 votes

How to simulate atomic scattering from solid walls at finite temperature for a particles in a box simulation?

Whatever scattering mechanism you choose must respect detailed balance in equilibrium: on average, the number of particles hitting a patch of the wall at a given angle and velocity must equal the ...
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  • 171
5 votes

How to simulate atomic scattering from solid walls at finite temperature for a particles in a box simulation?

Since no one has responded with expertise, I'll attempt a speculative answer here. To my mind, the simplest model of the atoms on the surface of the walls would be an ensemble of independent ...
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5 votes

Temperature effect on elastic constant using VASP

It is always better to write your own code to get elastic constants. For example , In case of cubic system, we need three types of distorsion to unit cell. Now elastic constant is simply slope of ...
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  • 3,269
5 votes

Is there an upper limit of temperature after which the quasi-harmonic approximation (QHA) fails?

The starting point of most calculations is the Born-Oppenheimer approximation, which separates the electronic and nuclear degrees of freedom. The electronic structure problem is then solved using a ...
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5 votes

Reaction rate estimation for relatively complex reactions

Relatively big systems can be treated with fragmentation methods that allow one to reduce the cost of the overall computation by using the most accurate and/or expensive approach on the most relevant ...
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4 votes

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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3 votes

On the nature of zero-point energy (ZPE)

The Born-Oppenheimer (BO) approximation works well at high temperatures (far from 0 K), but the quantum nature of the nuclei (i.e. the zero-point energy) is an important consideration at low ...
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3 votes

How to calculate temperature dependent phonon band structure in VASP

You can try the library TDEP, which has an example to calculate Phonons dispersions as a function of temperature.
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2 votes

Temperature effect on elastic constant using VASP

The following paper is quite nice, in my opinion: Shang et al., Temperature-dependent elastic stiffness constants of α- and θ-Al2O3 from first-principles calculations, J. Phys. Condens. Matter 22 (...
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2 votes

Does the thermal evolution of molecular structures critically affect the validity of the calculated magnetic anisotropy?

Not always the research pipeline is from experimental to theory. The group of Professor Artem Oganov had very interesting results where they started predicting theoretical structures (at extreme ...
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