Among computational chemistry methods, quantum mechanics calculates geometries and electronic structures with accuracy especially for systems with electronic delocalization. The use of a multiconfigurational approach is able to treat highly degenerated states such as those occurring at the transition state in some chemical reactions. Moreover, an accurate description of potential energy surfaces can be obtained with the evaluation of the dynamic electron correlation effects by this approach. Molecular properties range from simple dipole moments, vibrational frequencies or IR intensities to frequency dependent hyperpolarizabilities. Quantum chemical calculations are thus an attractive source of molecular descriptors which can be used in QSAR/QSPR studies and which can express all electronic and geometric properties of molecules. A survey and a comparison of the performance of free e-resources for semi-empirical and ab initio calculations is provided.
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http://dx.doi.org/10.1080/1062936032000169660 | DOI Listing |
Entropy (Basel)
November 2024
Beijing Academy of Quantum Information Sciences, Beijing 100193, China.
Variational quantum algorithms (VQAs) have shown strong evidence to gain provable computational advantages in diverse fields such as finance, machine learning, and chemistry. However, the heuristic ansatz exploited in modern VQAs is incapable of balancing the trade-off between expressivity and trainability, which may lead to degraded performance when executed on noisy intermediate-scale quantum (NISQ) machines. To address this issue, here, we demonstrate the first proof-of-principle experiment of applying an efficient automatic ansatz design technique, i.
View Article and Find Full Text PDFJ Am Chem Soc
April 2024
National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States.
Molecular lanthanide (Ln) complexes are promising candidates for the development of next-generation quantum technologies. High-symmetry structures incorporating integer spin Ln ions can give rise to well-isolated crystal field quasi-doublet ground states, i.e.
View Article and Find Full Text PDFJ Chem Phys
April 2024
Department of Chemistry and The PULSE Institute, Stanford University, Stanford, California 94305, USA and SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
Electronic structure theory, i.e., quantum chemistry, is the fundamental building block for many problems in computational chemistry.
View Article and Find Full Text PDFACS Omega
December 2022
Department of Chemistry, Indian Institute of Technology Indore, Simrol, Khandwa Road, Indore453552, India.
J Chem Phys
May 2022
Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
Bonding energies play an essential role in describing the relative stability of molecules in chemical space. Therefore, methods employed to search chemical space need to capture the bonding behavior for a wide range of molecules, including radicals. In this work, we investigate the ability of quantum alchemy to capture the bonding behavior of hypothetical chemical compounds, specifically diatomic molecules involving hydrogen with various electronic structures.
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