8/26/2020 0 Comments Application Of Quantum Chemistry
A quantum bit (qbit) can have any value between 0 and 1 but is only 0 or 1 when measured (somewhat like z-projection of angular momentum).A quantum chemical study of the protonation of.Quantum Chemistry.
Applications of Green Chemistry Principles in Agriculture Chemistry. Quantum Algorithms for Quantum Chemistry based on the sparsity of. Applications of Quantum. Chemistry. H E. Efforts underway to. Applications of Quantum Chemistry H E Areas of Application Explaining observed phenomena (e.g., spectroscopy) Simulation and modeling: make predictions New techniquesdevices use special quantum properties Q.M. Required to Explain Many Observed Phenomena Blackbody radiation Photoelectric effect: makes no sense without the idea of photons H atom spectrum (and other spectra) explained extremely well by Q.M. Two-slit experiment: interference patterns caused by wave-like properties of matter Many others Simulation and Modeling Electronic Structure Theory: Solve for electronic Schrdinger Equation, get electronic properties and potential energy surfaces. Dynamics: Solve for motion of nuclei on the potential energy surfaces. Important for detailed understanding of mechanisms. Electronic Structure Theory Electronic wavefunction and its derivatives give Dipole moment, polarizability, Spectra: electronic, photoelectron, vibrational, rotational, NMR, Equilibrium geometry is one with minimum energy Electronic Structure Methods Method Semiempirical Accuracy Low Max atoms 2000 Hartree-Fock Medium Density Functional Perturbation High Variation Methods 500 Coupled-Cluster 20 Very High 50 High-Accuracy Quantum Chem Typical accuracy of coupled-cluster methods Property Accuracy Bond lengths 0.004 Bond angles 0.03 Vibrational frequencies 2 Dipole moments 0.05 D Relative energy 1.5 kcalmol Example Applications Predictingconfirming spectra Sructuresenergies of highly reactive molecules Interaction between possible drugs and enzyme active sites Computational materials science Interstellar Molecule Spectra 1-Silavinylidene has been predicted to be abundant in interstellar space H CSi: H Could search for it if we knew what its microwaveinfrared spectra looked like Bengali and Leopold performed tricky experiments and requested theoretical confirmation. Phys. Chem. 99, 1949 (1995). Vibrational Spectra of SiC2H2 Species Maier et al. Maier et al. Angew. Sherrill et al. J. Am. Chem. Soc. 118, 7158 (1996). Theory Shows Silacyclopropyne Seen Highly Reactive Systems Many molecules are hard to study experimentally: e.g., radicals, diradicals, highly strained molecules. Theory can be helpful in understanding such systems. N8: Possible Rocket Fuel vFirst studied theoretically. Leininger, Sherrill, and Schaefer, J. Phys. Chem. 99, 2324 (1995). Design of New Molecules Often need to design a molecule for a specific purpose (e.g., N8 for rocket fuel). Theory is useful for narrowing down the list of candidate molecules. Ruling out bad candidates early saves time: no need to synthesize something which wont work. Christoph Fahrni Need a way to track Cu(I) ions in the body to understand their biochemical role Use theory to predict structures and spectra of possible Cu(I) probes Rational Drug Design Take structure of enzyme and model interaction with possible drugs Often uses classical mech. Model of candidate inhibitor for HIV-1 protease. Physical Computing Group, Rice U.) Computational Materials Science Study larger systems with more approximate methods (DFT at best). Peter Ludovice (CHE): simulation of polymers. Prof. Uzi Landman (PHYS): simulation of surfaces and interactions of surfaces. Ni tip on Au surface New DevicesTechniques Quantum Computing: The ultimate parallel computer. Potentially billions of times faster than conventional computers. Quantum Cryptography: Use Uncertainty Principle to keep out eavesdroppers. Quantum Computing Conventional computers are being improved by smaller and smaller chips. This will end when the features become so small that quantum effects become important (10-15 years). Power of Quantum Computing Before the wavefunction collapses, quantum system is in multiple states simultaneously --2n states for n qbits (very large). Application Of Quantum Chemistry How To Use ThisTake advantage of this to process in parallel: In 1994, Peter Shor (ATT) showed how to use this to factorize numbers (important in encryption). Factoring 400 digits might take 1 year on quantum computer, billions of years on supercomputer Quantum Computing Scheme Basic idea: take advantage of special quantum properties of superposition and measurement.
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