Messages

31

General Questions and Answers / Global minimum for bulk-reg

« on: July 14, 2016, 15:07 »

Hi,

The total energy of a functionalized carbon system of mine was obtained as follows.

total energy with k points 150 and mesh cut-off 350= -12053.11237 eV
total energy with k points 150 and mesh cut-off 350 after creating bond length change= -12053.12018 eV
Is it under global minimum???

32

General Questions and Answers / Magnetic moment

« on: May 26, 2016, 14:55 »

Hi

How to calculate magnetic moment through atk 12.8.2 version with parallised codes???
Kindly provide the scripts

Highly appreciated

Regards
GJK

33

General Questions and Answers / Restarting a calculation-chk file or trajectory path

« on: May 26, 2016, 13:34 »

Hi,

When I performed geometry optimization it was cut off suddenly due to a power problem.

I have saved the trajectory(35 images) and also located the chk file from the tmp folder(our jobs are running on the newly implemented mpich paralliesed codes)

Which is best to re run the optimization chk file or the trajectory 35th image with a force component of 0.17 eV/A???

or

is it ok to restart the calculation newly from the chk file???

34

General Questions and Answers / Volume

« on: May 19, 2016, 14:39 »

Hi,

The polarisation can be calculated using dipole moment/volume.

The volume that we get in the lattice parameters is the volume of the periodic structure(including super cell volume) or the over all volume of the structure alone???

35

General Questions and Answers / k points for bulk

« on: May 19, 2016, 14:12 »

Hi,

Is k points vs total energy is sufficient to find the global minimum of energy??

Some authors are reporting zero imaginary frequency to prove that our structure is at global minimum.How to calculate the frequencies(imaginary) using ATK???

Your reply is highly appreciated.

36

General Questions and Answers / Re: Electric field gradient tensor from quadrupole moment script-reg

« on: September 23, 2015, 17:18 »

1. The default calculator in ATK-DFT module uses the norm-conversing pseduopotential, which doesn't provides the charge density of core electrons. To restore the charge density of core region, additional computational techniques are needed, as done in the  GIPAW package (http://www.gipaw.net/theory.html).
2. The example demonstrated in http://quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.electrondifferencedensity.html is done for the estimation of monopole, dipole, and quadropole of a molecule. But for such calculations for a bulk system without vacuum region, some caution should be taken care of because  the position operator is ill-defined in periodic systems.

Dear sir,

If this is the answer then what does the quarupole moment calculated through ATK signify???
Is it the field gradient tensor for the entire molecule???

37

General Questions and Answers / Eigen states of graphene nanoribbon

« on: September 5, 2015, 14:52 »

Hi,

Eigen states have been given for a water molecule.
1. Can we apply the same principle to calculate the eigen states between any two atoms in functionalized graphene???
2.The change in eigen states from localized s wave function to p wave wave function at the Fermi energy  between will be proportional to the reactivity. Am I correct??

This question came in picture as we have only Bloch wave function analysis for graphene nanoribbon.

38

General Questions and Answers / Re: Electric field gradient tensor from quadrupole moment script-reg

« on: September 5, 2015, 09:03 »

Dear Zh ,

Thanks for the reply.But here is the usage exampe http://www.sciencedirect.com/science/article/pii/S0749603612001449
where they have calculated EQR on independent atoms. ATK  is a powerful tool then why not we? Also already as per the advice of Dr.Anders I have tried for convergence tests in molecule and bulk configurations which gave approximately the same results...

I have some clues; you said it is difficult to compute the charge density of independent core region.My question: Is it possible to use the Mulliken report for the excess charges on each atom and compute volume charge density as excess charge on each atom divided by volume occupied by each atom.

We have total volume for the bulk configuration how to compute volume on each atom???

Then we get EFG tensor on each atom.Am I correct???

39

General Questions and Answers / Electric field gradient tensor from quadrupole moment script-reg

« on: August 13, 2015, 19:57 »

Hi,
We have the script provided by Dr.Anders http://quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.electrondifferencedensity.html
for finding quadrupole.

The script is for finding qzz(electric field gradient) for a complete system.Is it posssible to provide a quadrupole script for finding qzz on independent atoms in a system.If you could provide we can compute NQR through ATK wonderfully.

I have raised the question for NQR-qzz; but the answers came for finding qzz through other software packages.That time I was completely shielded off from Dr.Anders beautiful script for monopole,dipole and qudrupole.With the existing script we have quadrupole calculation for complete system but not independent atoms.

Thanks in advance

40

General Questions and Answers / Band index and Bloch states

« on: August 10, 2015, 20:03 »

Hi,

The bloch states tutorial is calculated for ZGNR complete unit cell for the valence and conduction band.

How to calculate the bloch states between any two atoms in doped or bare ZGNR??

Eg If we want to compute the bloch states for nitrogen and carbon atom (nitrogen is doped in ZGNR) THEN HOW TO COMPUTE IT???

41

General Questions and Answers / Molecular energy spectrum and band structure

« on: August 10, 2015, 18:17 »

Hi,

Why molecular energy spectrum and band structure giving two different results?

The band structure showing metallic character for ZGNR while the molecular energy spectrum reveals a band gap.What is the difference between the two??

What should we prefer while calculating the  HOMO-LUMO gap for a bulk; is it molecular energy spectrum or band structure?

42

General Questions and Answers / Electric field tensor

« on: August 6, 2015, 19:33 »

Hi,

To determine the electronic property of a material we can do NQR studies(nuclear quadrupole resonance). How to calculate the electric field tensor qzz using ATK for a bulk

43

General Questions and Answers / POLAR SURFACE AREA

« on: April 17, 2015, 21:25 »

Hi,

How to calculate the polar surface area for carbon nanostructures using ATK?

44

General Questions and Answers / Re: optical spectrum-reg

« on: April 17, 2015, 05:59 »

For isotopic material the value will be same at zero frequency.

For anisotropic we are gettting three values for the tensor at zeroth frquency. Should we average like
1/3(epsilon xx+epsilon yy+epsilon zz) or is there any other formula???

Thanks in advance

45

General Questions and Answers / optical spectrum-reg

« on: April 13, 2015, 09:15 »

We have the tutorial for calculating the static dielectric constant for isotropic materials from optical spectrum

What is the formula for calculating the same for anisotropic materials from optical spectrum, where we have varying values along x y z directions

Thanks in advance