A second-order extension of the Kohn-Sham total energy in density-functional theory (DFT) with respect to charge density fluctuations serves as the foundation for the density functional based tight binding (DFTB) approach.
What is DFTB method?
- The density functional based tight binding (DFTB) electronic structure method was used to study the clusters of bare TiO2 and TiO2 with linked organic ligands modeling polyorganic composites used as photocatalytic materials. 
 - The results were compared to those obtained from B3LYP/6-31G(d,p) calculations, semiempirical methods PM6 and PM7, and available experimental data. 
 - It was discovered that the highly scalable DFTB approach produces outcomes that are nearly on the level of theory B3LYP/6-31G(d,p).
 - The trans3d set more accurately reproduces the energies of the composite material production in polycondensation processes, but the corrected version of the tiorg DFTB parameter set (tiorg-smooth) performs better for structural parameter estimations. 
 - The tiorg-smooth and trans3d settings perform better than the matsci set in some way. Studies of adsorption complexes of bare TiO2 clusters can be conducted using the tiorg-smooth and matsci sets.
 
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Answer is B. Releases heat and is exothermic
        
             
        
        
        
The correct answer is:
TRIGONAL PYRAMIDAL
        
             
        
        
        
Answer:
The 3rd choice
Explanation:
A strong acid ionises COMPLETELY in water to produce high concentration of hydrogen ions
A weak acid ionises PARTIALLY in water to produce low concentration of hydrogen ions