Density functional theory (DFT) is a quantum mechanical model used to estimate the electronic structure of molecules and condensed matter. In broad terms, DFT works by treating all the electrons in the system as a single electron density, and computing physical quantities of interest as functionals ...

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636 views

What is the current state of research into $v$-representability?

In their proof, Hohenberg and Kohn (Phys Rev 136 (1964) B864) established that the ground state density, $\rho_\text{gs}$, uniquely determines the Hamiltonian. This had the effect of establishing an ...
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2answers
851 views

B3LYP vs PBE functionals for conjugated organic systems

Two of the most popular (exchange and correlation) functionals for density functional theory are B3LYP and PBE. Out of the people I've worked with / learned from, mostly the computational chemists ...
4
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2answers
631 views

Implementing simple atom model using density functional theory (DFT)

I am trying to write computer code which will find the energy and density function for an atom with $Z$ protons and $N$ electrons. I am working in 1D for simplicity and would like to make the overall ...
3
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1answer
159 views

How does a unique electron probability distribution correspond to one wavefunction?

I'm reading the Wikipedia article on DFT, and it says that there is a one-to-one correspondence between the ground state particle density $$n_0(\vec{r}) = N \int \text{d}^3 r_2 \int \text{d}^3 r_3 ...
3
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1answer
173 views

Antisymmetric functions as Slater determinants

Can any antisymmetric function, i.e., a function of $N$ spatial-plus-spin variables $\{x_i\ | \ i= 1, \ldots, N\}$ satisfying $$ \psi(x_1,\ldots, x_i, \ldots, x_j, \ldots, x_N) = -\psi(x_1,\ldots, ...
2
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2answers
627 views

Coulomb potential energy functional derivative

I'm having problem understanding how to compute a functional derivative when it's involved more than one integral, such as the coulomb potential energy functional: $$ J[\rho] = \frac 12\int ...
2
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1answer
86 views

How to calculate excluded volume in Onsager's hard-rod model?

Can somebody please provide a derivation of how to calculate excluded volume of two rods with angle of intersection being $\gamma$. rods are cylinders, capped with semi-spheres. Onsager theory of hard ...
2
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1answer
100 views

DFT breakdown for effects that depend on phase?

Given the Hohenberg-Kohn theorem, a given ground-state density uniquely defines all ground state properties, because in principle the external potential $V_{ext}$ can be understood as a functional of ...
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1answer
260 views

DFT for bandstructure

Density Functional Theory (DFT) is not appropriate in predicting the band gap of the materials. However, which functional gives close value to the experimentally observed band gap of semiconductors? ...
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1answer
313 views

Constrained-search formulation of DFT: by Levy or by Levy-Lieb

I'm a bit puzzled about how to give the right references for the constrained-search formulation of DFT. Till now, I only heard it being called "Levy constrained-search" but came about some papers and ...
1
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1answer
149 views

Dyson Schwinger equation

given the Dyson equations $ \frac{\delta S}{\delta \phi(x)}\left[-i \frac{\delta}{\delta J}\right]Z[J]+J(x)Z[J]=0 $ is true that they are a solution or differential representation of the Generating ...
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1answer
51 views

Kohn-Sham equations from variational principle

I'm trying to understand how the Kohn-Sham equations arise from the variational principle, failing. I think my problem is the inability to apply the variational principle. Or, I lack some crucial ...
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29 views

Computer coding of Perdew Burke and Ernzerho (PBE) method

I have been assigned the task to write a computer code to implement the Perdew Burke and Ernzerhof (PBE) method. Does anyone know a good reference which can make the coding of this method easier?
0
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1answer
30 views

DFT Calculations, Atomic Ionization Potentials — Which Exchange-Correlation Functional to Use, to Preserve Koopmans' Theorem?

I have a program which can perform density-functional calculations for atoms, given a density functional. Of course the simplest form of exchange potential to use is one relevant for a uniform ...
0
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1answer
160 views

Dopant Charge Transfer and Fermi Level shift

When a system has a dopant, how much does the Fermi level shift? For example, say a finite concentration of substitutional dopants replace some bulk atoms, and each has one extra electron. Ignore any ...
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0answers
20 views

Couting the occupied states in band structure

I work with several dft codes and I have produced the band structures of some doped semiconductors with their plots. The problem I have is that I do not know how I can analyze the band structure and ...
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0answers
11 views

Aluminum magnetic moment in ZnO

I have made a density functional theory on calculation zno 2x2x2 super cell and I have substituted one of the Zn atoms with Aluminum and did spin polarized calculation. I expected that the unpaired ...
0
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0answers
23 views

How to model a nonperiodic supercell as a periodic one?

Some researchers use Hydrogen atom termination, to model a non periodic finite sized 2D and 1D structures as periodic one. How far this approach is useful in predicting the properties of periodic ...