Questions tagged [quantum-dynamics]

Questions about quantum dynamics methods (MCTDH, t-DMRG, Feynman integral dynamics, etc.), or in some cases about quantum dynamics itself. Quantum dynamics is usually the dynamics of wavefunctions, density matrices, reduced density matrices, Wigner functions, or properties/expectation-values.

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Time Evolution of the Hartree-Fock Wave Function

The Hartree-Fock Hamiltonian is given by $$ \hat{H} = \sum_i \hat{h}_i + \frac{1}{2}\sum_i\sum_j \left[\hat{J}_{ij} - \hat{K}_{ij}\right] $$ and by choosing a basis, the Hamiltonian can be written in ...
Peter234's user avatar
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5 votes
0 answers
81 views

How can one determine the time-step for imaginary time evolution?

The real-time evolution of a quantum system described by the state $\psi(t)$ is formally given by, $$ \psi(t+\Delta t) = \exp^{- i \hat{H} \Delta t / \hbar} \psi(t)\tag{1}$$ For dynamical simulations ...
squareroottwo's user avatar
15 votes
3 answers
2k views

Can DFT simulate chemical reactions?

I was wondering, can you simulate the chemical reaction between two or more molecules using DFT? If not, what numerical method is usually used for this?
Carlos Andrés del Valle's user avatar
5 votes
0 answers
235 views

What's the role of Berry curvature in quantized Hall effects? [closed]

Cross-posted and answered at Physics.SE. The quantized versions of the Hall effect include (ignoring fractional quantum Hall effect): Quantum Hall effect; Quantum anomalous Hall effect; Quantum spin ...
Jack's user avatar
  • 14.9k
7 votes
0 answers
68 views

How to calculate electronic circular dichroism (ECD) spectra from MCTDH? [closed]

Electronic circular dichroism (ECD) spectra is commonly used in organic chemistry to characterize chiral molecules. Here the question is how to simulate ECD spectra using MCTDH (Multi-configurational ...
Paulie Bao's user avatar
  • 3,813
4 votes
1 answer
195 views

How to calculate state population from MCTDH?

In this reference, the author investigates electronic population dynamics from a MCTDH calculation. My question is how to generate state populations over time from an MCTDH calculation? Is there a ...
Paulie Bao's user avatar
  • 3,813
12 votes
1 answer
273 views

What are some of the biggest theoretical and computational challenges in Condensed Phase Chemistry?

What are some of the biggest open-questions / challenges in Condensed Phase theory and computation? What efforts are being done to answer them? I realize Condensed Phase chemistry is a huge field, but ...
epalos's user avatar
  • 4,709
15 votes
1 answer
784 views

How exact is DFT, really?

It is often claimed (e.g. here), that Density Functional Theory is in principle exact. This seems to be a very strong statement to me. Are all current limitations only of a technical nature rather ...
Wouter's user avatar
  • 333
22 votes
5 answers
4k views

References for Molecular Dynamics?

I am new to the world of Molecular Dynamics (zero practical experience), and I know that a starting point to really go into the back-bone of MD is Statistical Mechanics (took a semester course in ...
epalos's user avatar
  • 4,709
10 votes
1 answer
219 views

What is the "overcoherence problem" in Ehrenfest dynamics?

I am a novice in Ehrenfest dynamics and would like to know why Ehrenfest dynamics suffers from the "overcoherence problem"?
Meilani Wibowo's user avatar
5 votes
0 answers
74 views

What is the difference between Ehrenfest dynamics and Born-Oppenheimer Molecular Dynamics? [duplicate]

What is the fundamental difference(s) between Ehrenfest dynamics and Born-Oppenheimer MD? Also, in what situation(s) or case(s) one is preferred than the other one?
Meilani Wibowo's user avatar
11 votes
1 answer
290 views

What are the types of Quantum Molecular Dynamics (QMD)?

In similar spirit to recent questions on Quantum Monte Carlo, ab-initio Molecular Dynamics, types of SCF, and others, I would like to ask: What are the types of Quantum Molecular Dynamics (QMD)? As I ...
epalos's user avatar
  • 4,709
19 votes
1 answer
302 views

Quadrature over three Euler Angles for orientation averaging

Does anybody know about an accurate quadrature rule over three Euler angles $\theta, \phi, \chi$? I am trying to calculate the average value of an arbitrary function $f(\theta, \phi, \chi)$ for a ...
Emil Zak's user avatar
  • 896
6 votes
2 answers
172 views

How is MCTDH derived?

In the multi-configurational time-dependent Hartree (MCTDH) method, the equation of motion is derived from the time-dependent Schrödinger equation by substituting the wavefunction ansatz expanded in a ...
Paulie Bao's user avatar
  • 3,813
9 votes
1 answer
196 views

How to construct the single particle function (SPF) basis in MCTDH?

In the multi-configurational time-dependent Hartree (MCTDH) theory, one essential step that reduces the memory and time cost is to form a single particle function (SPF) basis ansatz as shown in ...
Paulie Bao's user avatar
  • 3,813