The molecular structure of the stable conformation of phosphonic acid in gas phase has beencomputed by employing complete geometry optimization in Density Functional Theory(DFT) methods. The methods used for calculations are B3LYP, BP86 and B3PW91 that havebeen studied in two series of basis sets: D95** and 6-31+G(d,p) for hydrogen and oxygenatoms; LANL2DZ for phosphorus. Bond lengths and angle...

We present an accurate and efficient technique for calculating thermal X-ray absorption fine structure (XAFS) Debye-Waller factors (DWFs) applicable to crystalline materials. Using Density Functional Theory on a 3 3 3 × × supercell pattern of MnO structure, under the nonlocal hybrid B3LYP functional paired with Gaussian local basis sets, we obtain the normal mode eigenfrequencies and eigenvecto...

The performances of the B3LYP density functional in the computation of harmonic and anharmonic frequencies were tested using 14 standard basis sets of double and triple zeta quality for a set of semirigid molecules containing from 4 to 12 atoms. The quality of the results is assessed by comparison with the most reliable computations available in the literature. The study reveals that the relati...

The Infrared spectrum of L-phenylalanine L-phenylalaninium-benzoic acid (LPB) was recorded and analyzed in the region 4000–400 cm. Optimized geometrical structures and harmonic vibrational frequencies have been computed by the B3 based (B3LYP) density functional method using 6-31+G (d, p). The calculated first hyperpolarizability is comparable with the reported value of similar structures and m...

Ladder-type polymers, obtained by small modifications of the atomic structure of ladder-type polythiophene, are studied using density-functional theory calculations. Within the local-density and GW approximations, it is found that upon a simple substitution of the sulfur atoms by nitrogen and boron atoms, the band structure of the resulting polymer exhibits band overlap between the occupied and...

High level Density Functional Theory (DFT) using B3LYP/6-311++G(2df,2p)//6-311+G(d,p) calculations on the relative stabilities and structures of the neutral, protonated and deprotonated isorhodanine tautomeric forms are reported in the gas phase and solution. Gas phase and solution B3LYP calculations predict that the oxo/thione tautomer is the most stable one in all cases. Comparison of the gas...

Electronic circular dichroism spectra transition energies and intensities were modeled using the independent particle model within the Kohn-Sham theory. The data obtained were compared with higher level calculations and experimental data. Since the model describes main features in the experimental spectra qualitatively well, it is being proposed as a fast and efficient simulation technique for ...

Some theoretical properties were analyzed and compared with the experimental data for Tamoxifen molecule, a drug commonly used as complementary therapy for breast cancer. The molecular structure and some chemical reactivity parameters were calculated through Density Functional Theory using different functionals, including B3LYP, PBE0, PBEPBE, TPSS, TPSSh and the M05 and M06 density functionals ...

A theoretical study of possible metallization sites within polypeptide structures is reported. The study has involved performing density functional B3LYP calculations in order to describe the affinities of various amino acids and larger peptide fragments towards copper ions. The results obtained for small amino acid systems have been used in the theoretical analysis of feasible metallization si...

The B state excited resonance Raman scattering of tetraoxaporphyrin dication (TOP) was theoretically studied with DFT/TDDFT calculations and the sum-over-states approach of polarizability including both the A and B terms contributions. The resonance Raman spectra calculated with PBE1PBE, B3LYP, Cam-B3LYP, and B3LYP-D3 functionals are similar to each other in general, with PBE1PBE and B3LYP bein...