How to calculate the basis function energy from DFT programs?

In summary, the DFT program used for calculating the density of states of electrons from metallic clusters does not provide information on the energy values of the basis function orbitals. However, it is possible to use the full Hamiltonian to obtain an average energy of the system by taking the expectation value for a basis function. It is important to note that basis functions are mathematical constructs and not physical entities with energy values.
  • #1
peter308
15
0
Dear all:

I need to calculate the density of states of electrons from metallic clusters. I ran a DFT program and output the mulliken population analysis datas, such as the following:


(I show only part of the data)

ATOM # 1

ORBITAL ALPHA OCCUPATION
5s 0.0061
6s 0.3406
7s -.0419
4py 0.0827
4pz 0.0827
4px 0.0827
5py 0.7021
5pz 0.7021
5px 0.7021
6py 0.2155
6pz 0.2155
6px 0.2152
4d-2 0.7892
4d-1 0.7898
4d+0 0.7906
4d+1 0.7895
4d+2 0.7909
5d-2 0.1637
5d-1 0.1635
5d+0 0.1633
5d+1 0.1637
5d+2 0.1633
6d-2 0.0397
6d-1 0.0409
6d+0 0.0405
6d+1 0.0399
6d+2 0.0395


However, the program seems not provide any information on energy value of the basis function orbitals, such as "6s" or "4d+2". I wonder how one can obtain it from the program?By the way, i use a software named "deMon2k" for doing dft calculations.I am appreciated if you could provide me with any ideas, thanks.



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Yen
 
Last edited:
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  • #2
peter308 said:
However, the program seems not provide any information on energy value of the basis function orbitals, such as "6s" or "4d+2". I wonder how one can obtain it from the program?
There is a fundamental misunderstanding here. Linear combinations of the basis functions are used to construct energy eigenstates (##\psi_j=\sum_i a_i\phi_i##). It is an odd question to talk about the energies of the basis functions; they are really only mathematical constructs.

That said, you can certainly take the full Hamiltonian for the system in question and operate it on a basis function (which will in turn be a linear combination of energy eigenstates ##\phi_j=\sum_i b_i \psi_i##). This will return a weighted list of energy eigenstates. You could get an average energy of the system by taking the expectation value of the Hamiltonian for a basis function ##\langle \phi_j|H|\phi_j\rangle##. But I'm not sure if that procedure would give you any useful information.
 

Related to How to calculate the basis function energy from DFT programs?

1. What is the basis function energy in DFT programs?

The basis function energy is the total energy of a system calculated using the density functional theory (DFT) approach. It represents the energy of the electrons in a system, taking into account the interactions between them and the surrounding nuclei.

2. How is the basis function energy calculated in DFT programs?

In DFT programs, the basis function energy is calculated by solving the Kohn-Sham equations, which are a set of mathematical equations that describe the behavior of electrons in a system. These equations are solved iteratively until the energy converges to a minimum value.

3. What factors can affect the accuracy of the basis function energy in DFT programs?

There are several factors that can affect the accuracy of the basis function energy in DFT programs, including the choice of basis set, the exchange-correlation functional, and the numerical parameters used in the calculations. The size and convergence of the basis set, as well as the quality of the functional, can also have a significant impact on the accuracy of the energy calculation.

4. How can I optimize the basis function energy in DFT programs?

To optimize the basis function energy in DFT programs, you can vary the parameters mentioned in the previous question, such as the basis set, exchange-correlation functional, and numerical parameters. It may also be helpful to compare the calculated energy with experimental data or results from other theoretical methods to ensure accuracy.

5. Is the basis function energy the only important quantity calculated in DFT programs?

No, the basis function energy is not the only important quantity calculated in DFT programs. Other important quantities include the electronic density, the electron density distribution, and the total energy of the system. These quantities are used to calculate other properties of the system, such as the molecular geometry, electronic structure, and reactivity.

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