This guy really deserves appreciation. After watching so many videos to learn DFT calculation as a beginner. I found this person's explanation really good. if you completely watch all his videos. It sure that you would learnt the basics of DFT calculation really well.
@@quantumguruji yes, I have opened the output file and seen the delocalization interactions of different atoms from bonding orbitals to antibonding orbitals but my question is how to differentiate which ones are sigma-*sigma and which ones are pi-*pi because it wasn't indicated on the output result
Thank you sir very much for your insightful videos. Can you please guide on the issue: Methane forms a T shaped complex with benzene (with its pi electron cloud), then how can i scan the distance of methane from the center of ring (benzene) to construct a potential energy curve? It will be great help.
The scissor operator is a common tool used in the field of solid-state physics and materials science to adjust the calculated electronic band structure of a material to match experimental results, particularly when there's a discrepancy between theory and experiment. It's often used when standard density functional theory (DFT) calculations underestimate the bandgap of a material. Here are the general steps to apply the scissor operator to calculate the bandgap: Perform Standard DFT Calculations: Begin by performing standard DFT calculations on the material of interest. DFT calculations provide an initial estimate of the electronic band structure, including the bandgap. However, DFT calculations often underestimate bandgaps due to the approximate exchange-correlation functionals used. Compare to Experimental Results: Obtain experimental data for the material's bandgap. This can be from techniques like optical spectroscopy or photoemission spectroscopy. Compare the calculated bandgap from your DFT calculations to the experimental value. Identify the Discrepancy: If the calculated bandgap is significantly lower than the experimental one, it indicates that your DFT calculation has underestimated the bandgap. Apply the Scissor Operator: The scissor operator is essentially a shift in the energy levels of the electronic structure to match the experimental bandgap. It involves raising the energy of the conduction band (unoccupied states) or lowering the energy of the valence band (occupied states) or both. The amount you shift these bands is determined empirically. For a smaller calculated gap: If the calculated bandgap is smaller than the experimental value, you need to apply a positive scissor shift. You can add a fixed energy amount to the conduction band minimum (CBM) or subtract the same energy amount from the valence band maximum (VBM), or do a combination of both. For a larger calculated gap: If the calculated bandgap is larger than the experimental value, you need to apply a negative scissor shift. In this case, you can subtract a fixed energy amount from the CBM or add the same energy amount to the VBM or a combination of both. Recompute the Band Structure: After applying the scissor operator, recompute the electronic band structure with the adjusted energy levels. This will give you a modified band structure with a bandgap that better matches the experimental value. Validate and Refine: Check if the adjusted bandgap aligns better with experimental data. You may need to iteratively refine the scissor shift until you achieve a satisfactory match between theory and experiment. Interpret Results: Once you have an electronic band structure with a bandgap that matches experimental data, you can analyze the properties of the material based on this adjusted electronic structure. It's important to note that the scissor operator is a somewhat empirical approach, and the specific shift value to use depends on the material and the quality of the DFT functional you're using. Therefore, it's crucial to cross-validate your results with other experimental data and consider factors like lattice relaxation and excitonic effects that might also affect the bandgap.
@@BinoyKSaha Hello Sir, Yes, it is generally acceptable to perform NBO analysis on a single-point energy calculated structure derived from a single crystal X-ray structure. However, be aware that the X-ray structure may not represent the exact gas-phase geometry, which can influence the NBO results.
Calculating charge transfer through Natural Bond Orbital (NBO) or Mulliken analysis involves analyzing the electronic density distribution between atoms in a molecule. Both methods provide insights into the charge distribution and the extent of charge transfer between atoms. 1. Obtain the Molecular Geometry: First, you need to have the molecular geometry of the system, typically obtained from a quantum chemistry software package like Gaussian, ORCA, or NWChem. 2. Perform Electronic Structure Calculation: Run a quantum mechanical calculation at an appropriate level of theory (e.g., DFT, HF, MP2) to obtain the electronic wavefunction and charge distribution. You'll need the electron density, orbital coefficients, and other relevant electronic structure information. Using NBO Analysis: 1. Perform NBO Analysis: Perform NBO analysis on the electronic structure results using software that supports NBO analysis, such as the NBO 6.0 program or a compatible package in your quantum chemistry software. NBO analysis provides natural bond orbitals and associated charge distribution information. 2. Extract Charge Transfer Information: NBO analysis will provide data on the charge distribution in the form of charge densities on atoms and bonds. You can identify charge transfer by comparing the charge densities on the donor and acceptor atoms. If the donor atom has a lower charge density than the acceptor atom, it indicates charge transfer from the donor to the acceptor. Using Mulliken Analysis: 1. Perform Mulliken Analysis: Perform Mulliken population analysis on the electronic structure results. Most quantum chemistry software packages provide the option to perform Mulliken analysis. 2. Extract Charge Transfer Information: In Mulliken analysis, you'll obtain atomic charges for each atom in the molecule. Charge transfer can be assessed by comparing the initial atomic charges (before interaction) and the final atomic charges (after interaction). The difference in charges indicates the amount of charge transfer. Note: It's important to keep in mind that both NBO and Mulliken methods have their limitations and may provide different results. NBO analysis often provides a more physically meaningful description of charge transfer, while Mulliken charges can be sensitive to the choice of basis set and the level of theory used. Additionally, the interpretation of charge transfer can be complex in systems with strong electron delocalization, and care should be taken when interpreting the results. It's also worth noting that there are other methods, such as Bader analysis (AIM), that provide a different perspective on charge transfer and electron density distribution.
@@varukolumahipal1330Pop=(NTO,SaveNTO) NTOs are generated when the Pop=NTO option is specified. The Pop=SaveNTO option tells Gaussian to replace the ground state orbitals normally in the checkpoint file with the computed NTOs.
Please I did NBO calculations. The transition from anti bonding orbital to another antibonding orbital gave a stabilization energy higher than that of bonding to antibonding orbital. Which of them should be regarded as the highest stabilization energy?
Typically, the interaction between bonding and antibonding orbitals (n → σ*, π → π*, etc.) leads to stabilization, with bonding orbitals serving as donors and antibonding orbitals as acceptors. However, when you observe a transition from one antibonding orbital (filled) to another antibonding orbital (empty) giving a higher stabilization energy than a transition from bonding to antibonding, this can be unusual but not impossible. This could occur due to strong orbital overlap, higher polarization, or other specific characteristics of the molecular orbitals involved. Generally, the higher stabilization energy should be regarded as the most significant, irrespective of whether it involves antibonding to antibonding or bonding to antibonding interactions. The highest stabilization energy represents the most effective donor-acceptor interaction. Therefore, in this case, the transition between antibonding orbitals yielding the higher stabilization energy would be considered more stabilizing. Hope it may help you.
gauravjhaa.blogspot.com/2024/03/nbo-analysis-and-hyperconjugation.html
This guy really deserves appreciation. After watching so many videos to learn DFT calculation as a beginner. I found this person's explanation really good. if you completely watch all his videos. It sure that you would learnt the basics of DFT calculation really well.
wonderful job, You are not holding back anything. Really appreciate the courage to share your knowledge without any insecurity. Regards
Thank you.
Thanks for this wonderful explanation.
please can you explain how to distinguish between which interactions are sigma and which interactions are pi
That will be in the output file...just have a look...NBO section
@@quantumguruji yes, I have opened the output file and seen the delocalization interactions of different atoms from bonding orbitals to antibonding orbitals but my question is how to differentiate which ones are sigma-*sigma and which ones are pi-*pi because it wasn't indicated on the output result
@@israelekoro8617 BD(1) means Sigma bond and BD(2) means pi bond. You will see BD(1) or BD(2) keywords in the output file.
@@quantumguruji thanks a lot.
You are a light to science
Sir, could you please make videos on pNLMOs / pNBOs or share smth relating to them, how to generate and all
Thank you sir very much for your insightful videos.
Can you please guide on the issue:
Methane forms a T shaped complex with benzene (with its pi electron cloud), then how can i scan the distance of methane from the center of ring (benzene) to construct a potential energy curve?
It will be great help.
Soon I'll put a video about scan calculation. Keep following the channel.
Please guide, how to apply scissor operator to calculate bandgap comparing to experimental results
The scissor operator is a common tool used in the field of solid-state physics and materials science to adjust the calculated electronic band structure of a material to match experimental results, particularly when there's a discrepancy between theory and experiment. It's often used when standard density functional theory (DFT) calculations underestimate the bandgap of a material. Here are the general steps to apply the scissor operator to calculate the bandgap:
Perform Standard DFT Calculations: Begin by performing standard DFT calculations on the material of interest. DFT calculations provide an initial estimate of the electronic band structure, including the bandgap. However, DFT calculations often underestimate bandgaps due to the approximate exchange-correlation functionals used.
Compare to Experimental Results: Obtain experimental data for the material's bandgap. This can be from techniques like optical spectroscopy or photoemission spectroscopy. Compare the calculated bandgap from your DFT calculations to the experimental value.
Identify the Discrepancy: If the calculated bandgap is significantly lower than the experimental one, it indicates that your DFT calculation has underestimated the bandgap.
Apply the Scissor Operator: The scissor operator is essentially a shift in the energy levels of the electronic structure to match the experimental bandgap. It involves raising the energy of the conduction band (unoccupied states) or lowering the energy of the valence band (occupied states) or both. The amount you shift these bands is determined empirically.
For a smaller calculated gap: If the calculated bandgap is smaller than the experimental value, you need to apply a positive scissor shift. You can add a fixed energy amount to the conduction band minimum (CBM) or subtract the same energy amount from the valence band maximum (VBM), or do a combination of both.
For a larger calculated gap: If the calculated bandgap is larger than the experimental value, you need to apply a negative scissor shift. In this case, you can subtract a fixed energy amount from the CBM or add the same energy amount to the VBM or a combination of both.
Recompute the Band Structure: After applying the scissor operator, recompute the electronic band structure with the adjusted energy levels. This will give you a modified band structure with a bandgap that better matches the experimental value.
Validate and Refine: Check if the adjusted bandgap aligns better with experimental data. You may need to iteratively refine the scissor shift until you achieve a satisfactory match between theory and experiment.
Interpret Results: Once you have an electronic band structure with a bandgap that matches experimental data, you can analyze the properties of the material based on this adjusted electronic structure.
It's important to note that the scissor operator is a somewhat empirical approach, and the specific shift value to use depends on the material and the quality of the DFT functional you're using. Therefore, it's crucial to cross-validate your results with other experimental data and consider factors like lattice relaxation and excitonic effects that might also affect the bandgap.
great videos
Thank you 💕
Is it OK to do NBO analysis on a single point energy calculated structure which has been obtained directly from a single crystal X-ray structure?
@@BinoyKSaha Hello Sir,
Yes, it is generally acceptable to perform NBO analysis on a single-point energy calculated structure derived from a single crystal X-ray structure. However, be aware that the X-ray structure may not represent the exact gas-phase geometry, which can influence the NBO results.
It will be very helpful for all of you make a demo video on scissor operator using CASTEP code available in material studio
How to calculate charge transfer through nbo or mulliken
Calculating charge transfer through Natural Bond Orbital (NBO) or Mulliken analysis involves analyzing the electronic density distribution between atoms in a molecule. Both methods provide insights into the charge distribution and the extent of charge transfer between atoms.
1. Obtain the Molecular Geometry:
First, you need to have the molecular geometry of the system, typically obtained from a quantum chemistry software package like Gaussian, ORCA, or NWChem.
2. Perform Electronic Structure Calculation:
Run a quantum mechanical calculation at an appropriate level of theory (e.g., DFT, HF, MP2) to obtain the electronic wavefunction and charge distribution. You'll need the electron density, orbital coefficients, and other relevant electronic structure information.
Using NBO Analysis:
1. Perform NBO Analysis:
Perform NBO analysis on the electronic structure results using software that supports NBO analysis, such as the NBO 6.0 program or a compatible package in your quantum chemistry software. NBO analysis provides natural bond orbitals and associated charge distribution information.
2. Extract Charge Transfer Information:
NBO analysis will provide data on the charge distribution in the form of charge densities on atoms and bonds. You can identify charge transfer by comparing the charge densities on the donor and acceptor atoms. If the donor atom has a lower charge density than the acceptor atom, it indicates charge transfer from the donor to the acceptor.
Using Mulliken Analysis:
1. Perform Mulliken Analysis:
Perform Mulliken population analysis on the electronic structure results. Most quantum chemistry software packages provide the option to perform Mulliken analysis.
2. Extract Charge Transfer Information:
In Mulliken analysis, you'll obtain atomic charges for each atom in the molecule. Charge transfer can be assessed by comparing the initial atomic charges (before interaction) and the final atomic charges (after interaction). The difference in charges indicates the amount of charge transfer.
Note: It's important to keep in mind that both NBO and Mulliken methods have their limitations and may provide different results. NBO analysis often provides a more physically meaningful description of charge transfer, while Mulliken charges can be sensitive to the choice of basis set and the level of theory used.
Additionally, the interpretation of charge transfer can be complex in systems with strong electron delocalization, and care should be taken when interpreting the results. It's also worth noting that there are other methods, such as Bader analysis (AIM), that provide a different perspective on charge transfer and electron density distribution.
@@quantumgurujiHello Sir I have some difficulties in NBO can you send contact number
Hiii sir could you help me howvto run NTO studies in gaussian software
@@varukolumahipal1330Pop=(NTO,SaveNTO)
NTOs are generated when the Pop=NTO option is specified. The Pop=SaveNTO option tells Gaussian to replace the ground state orbitals normally in the checkpoint file with the computed NTOs.
Please I did NBO calculations. The transition from anti bonding orbital to another antibonding orbital gave a stabilization energy higher than that of bonding to antibonding orbital. Which of them should be regarded as the highest stabilization energy?
Typically, the interaction between bonding and antibonding orbitals (n → σ*, π → π*, etc.) leads to stabilization, with bonding orbitals serving as donors and antibonding orbitals as acceptors. However, when you observe a transition from one antibonding orbital (filled) to another antibonding orbital (empty) giving a higher stabilization energy than a transition from bonding to antibonding, this can be unusual but not impossible. This could occur due to strong orbital overlap, higher polarization, or other specific characteristics of the molecular orbitals involved. Generally, the higher stabilization energy should be regarded as the most significant, irrespective of whether it involves antibonding to antibonding or bonding to antibonding interactions. The highest stabilization energy represents the most effective donor-acceptor interaction. Therefore, in this case, the transition between antibonding orbitals yielding the higher stabilization energy would be considered more stabilizing.
Hope it may help you.
@@quantumguruji Thank you,
Does this mean I should indicate the antibonding orbital to antibonding orbital transitn in my results table?
@@israelekoro8617 yes
Stephania Circle
How can calculate the NRT with NBO??
nbo6.chem.wisc.edu/ex_nrt.htm , www.mdpi.com/1420-3049/25/18/4052