نتایج جستجو برای: hf calculations
تعداد نتایج: 131751 فیلتر نتایج به سال:
The frequencies and intensities for the vibrational bands of absorption spectra hydrogen-bonded (D2CO)2 D2CO∙∙∙DF dimers, two D2CO∙∙∙(DF)2 trimers four (D2CO)2∙∙∙DF are calculated in MP2/aug-cc-pVTZ approximation with basis set superposition error taken into account. Anharmonic values spectral parameters were obtained using second-order perturbation theory. influence hydrogen bonds on was deter...
Most torsional barriers are predicted with high accuracies (about 1 kJ/mol) by standard semilocal functionals, but a small subset was found to have much larger errors. We created database of almost 300 carbon–carbon barriers, including 12 poorly behaved that stem from the Y═C—X group, where Y is O or S and X halide. Functionals enhanced exchange mixing 50%) worked well for all barriers. poor ac...
BACKGROUND To address the need for personalized prevention, we conducted a subject-level meta-analysis within the framework of the Heart "OMics" in AGEing (HOMAGE) study to develop a risk prediction model for heart failure (HF) based on routinely available clinical measurements. METHODS AND RESULTS Three studies with elderly persons (Health Aging and Body Composition [Health ABC], Valutazione...
ab initio calculations at hf/6-31g* level of theory for geometry optimization and mp2/6-31g*//hf/6-31g* for a single point total energy calculation are reported for the importantenergy-minimum conformations and transition-state geometries of 1, 3-diazacyclohepta-1, 2-diene (2) and 1, 3-diazacycloocta-1, 2-diene (3). the c2 symmetric twist-chair (2-tc)conformation of 2 is calculated to be 7.4 kj...
using hartree–fock (hf) and ِِdensity functional theory (dft) calculations the thermodynamic properties such as thermal energy , , thermal enthalpy , , thermal entropy , , thermal gibbs free energy , , heat capacity ,cv, and molecular structures of several species involving in keto↔enol tautomerism related to acetaldehyde (a), 5,5-dimethyl-1,3-cyclohexanedione (dimedone) and acetylacetone (aa) h...
hartree-fock (hf) and density functional theory (dft) methods employed to study the effect of conformational change on the 13c chemical shifts of 6-mono axial and equatorial substituted and 6,7-di axial-axial, equatorial-equatorial and axial-equatorial substitutedderivatives of 5,6,7,8-tetrahydrodibenzo[a,c]cyclo-octene. the geometry of the conformers have been optimized in the gas phase employ...
A Raman spectroscopic analysis revealed that π-conjugation does not reach saturation at least up to the octamer in long α-oligofurans and spreads over 14-15 furan units in the polyfuran. Comparing DFT calculations with experimental results suggests that a considerable amount of HF exchange is required to reproduce computationally the observed conjugation.
We present systematic direct ab initio dynamics studies of proton transfer in hydrogen-bond systems using the tautomerization in gas phase formamidine and its monohydrated complex as model reactions. The thermal rate constants were calculated using a canonical variational transition state theory (CVT) with multidimensional semiclassical tunneling corrections within a small-curvature ground-stat...
Density fitting (DF), also known as the resolution of identity (RI), is a widely used technique in quantum chemical calculations with various types atomic basis sets─Gaussian-type orbitals, Slater-type well numerical orbitals─to speed up density functional, Hartree–Fock (HF), and post-HF calculations. Traditionally, custom auxiliary sets are hand-optimized for each orbital set; however, some au...
نمودار تعداد نتایج جستجو در هر سال
با کلیک روی نمودار نتایج را به سال انتشار فیلتر کنید