# Dr. Fabio PICHIERRI's Home Page

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*Modeling Complex Molecules and Materials with Electronic Structure Calculations*

My research activity is concerned with the study of the structural and physico-chemical properties of complex molecules and their aggregates using electronic structure calculations.
The systems investigated range from polyatomic molecules that are characterized by intriguing structures (e.g. natural products, macrocycles, clusters, etc.) to proteins. Special enphasis is
placed on the interplay between molecular and electronic structure and function. The chemical phenomena investigated include (bio)molecular recognition, host-guest interactions, reaction mechanisms,
conformational properties, and the role played by the electronic structure of proteins in biology and biochemistry. Insights into the nature of molecular-level phenomena that occur in chemistry
and biology are searched through the application of modern computational quantum chemistry methods (ab initio and semiempirical MO, DFT). Chemical bonding and intermolecular
interactions are investigated with the aid of the Quantum Theory of Atoms in Molecules (QTAIM).

### Recent results:

H2-storage by halide anions
Quantum Proteomics
[n]ivyanes, n=2-8
Ligh-harvesting complex 2 (LH2)
Charybdotoxin
Potassium channel's macrodipole
Sulfilimine bonding
Octatetranyl anion

### Collaborative studies:

I enjoy scientific collaborations with experimental and computational groups in Japan and worldwide.

### Computational Chemistry and Molecular Modeling:

Computational chemistry is the field of chemical research concerned with the use of computers and specialized software to investigate the properties of molecules, supramolecular assemblies as well as chemical reactions and other complex molecular-level phenomena.
When the polyatomic systems under investigation are modeled using the principles of Quantum Mechanics, then we use the terms Electronic Structure Calculations or Ab Initio Quantum Chemistry.
The starting point of these studies is represented by the numerical solution of the time-independent non-relativistic Schroedinger equation according to the Hartree-Fock (HF) method.
Developments beyond the HF approximation (which neglects the correlated motion of electrons, i.e. electron correlation) have been achieved with both post-HF methods and Density Functional Theory.
On the other hand, when molecules are treated as classical objects (ball and spring model) while neglecting the physics of electrons, then we use the term Molecular Mechanics (MM).
The inclusion of Newton's equations of motion to model molecular systems extends MM to the field of (classical) Molecular Dynamics (MD) simulation. The combination of MD with electronic structure theory allows one to perform Ab Initio MD or First-Principles MD calculations. The Car-Parrinello method is one of the most popular methods in this category.
The integration of Quantum Chemistry with dynamics and Statistical Mechanics constitutes the core of Theoretical Chemistry .
The general term Molecular Modeling refers to the combined use of the above methods with Molecular Graphics tools in the study of molecular systems.
The use of computers in Chemistry is, however, not limited to studying the electronic structure of polyatomic molecules but comprises also applications in the fields of Analytical Chemistry, Drug Design, Chemical Crystallography, and so on. The terms Cheminformatics , Chemical Computing, and Computer-Aided Chemistry are also in common use although they do not necessarily imply the use of quantum mechanical methods.

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*Learning never exhausts the mind (Leonardo da Vinci)*