Dr. Gaurav Jhaa Blogs

 In Gaussian, NBO (Natural Bond Orbital) calculations are used to analyze the bonding patterns within molecules based on their electronic structure. NBO analysis provides insights into the nature of chemical bonding, including the characterization of bond types, lone pairs, and delocalization effects. Here's how you can perform an NBO calculation in Gaussian: Specify the NBO Keyword: To request NBO analysis in Gaussian, you need to include the "NBO" keyword in your input file. This instructs Gaussian to perform the NBO calculation as part of the electronic structure calculation. Perform an Electronic Structure Calculation: Before running the NBO analysis, you typically perform an electronic structure calculation (e.g., Hartree-Fock, DFT, MP2, etc.) to obtain the molecular orbitals and electron density. The type of calculation you choose depends on your specific research question or the level of theory appropriate for your system. Input Example: Here's an example of ho...

 Non-covalent interactions are important in understanding the behavior of molecules and materials in chemistry and biology. These interactions include hydrogen bonds, van der Waals forces, electrostatic interactions, and more. Calculating and analyzing non-covalent interactions can be crucial for predicting molecular structures, binding affinities, and other properties. Here's a general guide on how to calculate and analyze non-covalent interactions: 1. Software and Tools: You'll need specialized software or tools to perform quantum mechanical calculations or molecular dynamics simulations. Some popular options include Gaussian, DFT (Density Functional Theory) programs, and molecular modeling software like VMD, PyMOL, and Gaussian. 2. Geometry Optimization: Start by optimizing the geometry of the molecules or complexes of interest. This involves finding the lowest energy structure by minimizing the potential energy surface. 3. Identify Non-Covalent Interactions: Once you have o...

#CASTEP #dmol3 #nanomaterials #dft #dftcalculations #quantumchemistry #dftvideos #dfttutorials #materialsstudio #PES #Gaussian #Gaussview #spartan #forcite #quantumguruji #gauravjhaa #homolumo #dftstudy A set of standard basis sets is stored internally in Gaussian; these basis sets may be specified by including the appropriate keyword within the route section for the calculation. The Gen keyword allows a user-specified basis set to be used in a Gaussian calculation. It is used in place of a basis set keyword or a density-fitting basis set keyword. In this case, the basis set description must be provided as input (in a separate basis set input section). Gen may be analogously used to specify an alternate density fitting basis set (see the examples). The GenECP variation may be used to read in both basis functions and ECPs; it is equivalent to Gen Pseudo=Read. It is designed for use in ONIOM calculations in which you want to use a general basis set with ECPs within one ONIOM layer.

  Gaussian Common Errors and Solutions Link Error Message L1 ntrex1 Illegal ITpye or MSType generated by parse QPErr L101 End of file in Zsymb Found a string as input There are no atoms in this input structure Symbol not found in Z-matrix Variable index is out of range (Case 1) Variable index is out of range (Case 2) Attempt to redefine unrecognized symbol L103 Error imposing constraints FormBX had a problem Maximum of*** iterations exceeded in RedStp Linear search skipped for unknown reason Inconsistency: ModMin= N Eigenvalue= MM L108 Variable has invalid number of steps L114 Error in INITNF L123 Delta-x Convergence NOT Met GS2 Optimization Failure L202 Problem with the distance matrix Atom too close Change in point group or standard orientation FO...