Approximate calculation of electronic structure of complex molecules by method of linear combination of valence orbitals of fragments

1984 ◽  
Vol 25 (3) ◽  
pp. 343-351 ◽  
Author(s):  
O. V. Sizova ◽  
V. I. Baranovskii ◽  
G. B. Perminova ◽  
N. V. Ivanova
Keyword(s):  
Electronic Structure ◽  
Linear Combination ◽  
Approximate Calculation ◽  
Complex Molecules

scholarly journals LCAO Electronic Structure of Nucleic Acid Bases and Other Heterocycles and Transfer Integrals in B-DNA, Including Structural Variability

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4930
Author(s):  
Marilena Mantela ◽  
Constantinos Simserides ◽  
Rosa Di Felice
Keyword(s):  
Electronic Structure ◽  
Nucleic Acid ◽  
Linear Combination ◽  
Equation Of Motion ◽  
Diagonal Matrix ◽  
Coupled Cluster ◽  
Matrix Elements ◽  
Nucleic Acid Bases ◽  
Structural Variability ◽  
Transfer Integrals

To describe the molecular electronic structure of nucleic acid bases and other heterocycles, we employ the Linear Combination of Atomic Orbitals (LCAO) method, considering the molecular wave function as a linear combination of all valence orbitals, i.e., 2s, 2px, 2py, 2pz orbitals for C, N, and O atoms and 1s orbital for H atoms. Regarding the diagonal matrix elements (also known as on-site energies), we introduce a novel parameterization. For the non-diagonal matrix elements referring to neighboring atoms, we employ the Slater–Koster two-center interaction transfer integrals. We use Harrison-type expressions with factors slightly modified relative to the original. We compare our LCAO predictions for the ionization and excitation energies of heterocycles with those obtained from Ionization Potential Equation of Motion Coupled Cluster with Singles and Doubles (IP-EOMCCSD)/aug-cc-pVDZ level of theory and Completely Normalized Equation of Motion Coupled Cluster with Singles, Doubles, and non-iterative Triples (CR-EOMCCSD(T))/aug-cc-pVDZ level of theory, respectively, (vertical values), as well as with available experimental data. Similarly, we calculate the transfer integrals between subsequent base pairs, to be used for a Tight-Binding (TB) wire model description of charge transfer and transport along ideal or deformed B-DNA. Taking into account all valence orbitals, we are in the position to treat deflection from the planar geometry, e.g., DNA structural variability, a task impossible for the plane Hückel approach (i.e., using only 2pz orbitals). We show the effects of structural deformations utilizing a 20mer evolved by Molecular Dynamics.

Tight-binding calculations of electronic structure and resistivity of liquid and amorphous metals

1997 ◽  
Vol 491 ◽  
Author(s):  
S. K. Bose
Keyword(s):  
Electronic Structure ◽  
Transition Metals ◽  
Linear Combination ◽  
Tight Binding ◽  
Amorphous Metals ◽  
Recursion Method ◽  
Sources Of Error ◽  
Pseudopotential Approach ◽  
Structure Of Liquid

ABSTRACTWe discuss various aspects of calculating the electronic structure of liquid and amorphous metals using the recursion method and the tight-binding linear muffin-tin orbitals (TB-LMTO) basis. Resistivity calculations for such systems based on the Kubo-Greenwood formula and the TB-LMTO-recursion method are presented and compared with similar calculations based on the linear combination of atomic and atomic-like orbitals (LCAO) and the chemical pseudopotential approach. Results for amorphous Fe and Co and liquid Hg, Pd, and some 3d transition metals are presented. Sources of error in the calculation and ways to improve upon the present calculations are discussed.

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