نتایج جستجو برای: ab initio method

تعداد نتایج: 1666872  

2004
ERIC R. SCERRI

Quantum Mechanics has been the most spectacularly successful theory in the history of science. As is often mentioned the accuracy to which the gyromagnetic ratio of the electron can be calculated is a staggering nine decimal places. Quantum Mechanics has revolutionized the study of radiation and matter since its inception just over one hundred years ago. The impact of the theory has been felt i...

Journal: :The Journal of chemical physics 2015
Hitesh J Changlani Huihuo Zheng Lucas K Wagner

We propose a way of obtaining effective low energy Hubbard-like model Hamiltonians from ab initio quantum Monte Carlo calculations for molecular and extended systems. The Hamiltonian parameters are fit to best match the ab initio two-body density matrices and energies of the ground and excited states, and thus we refer to the method as ab initio density matrix based downfolding. For benzene (a ...

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه فردوسی مشهد - دانشکده علوم 1377

ترکیب -1فنیل -3آمینو -2بوتن -1 ون و کمپلکس مس (ii) آن تهیه و خالص شده اند. همچنین ترکیب فوق در موقعیتهای آمینو و آلیلی دوتره شده است . سپس طیفهای ارتعاشی مادون قرمز و رامان این ترکیبات تفسیر شده اند. علاوه بر این با استفاده از محاسبات ab initio در سطح hf/6-31g ساختمان ترکیب فوق و ایزومر ساختمانی آن، -4فنیل -4آمینو -3بوتن -2 ون، در دو طرف چاه پتانسیل هیدروژن کمینه و فرکانسهای ارتعاشی آنها محاسبه...

Journal: :Entropy 2012
Ramón F. Álvarez-Estrada

We consider non-equilibrium open statistical systems, subject to potentials and to external “heat baths” (hb) at thermal equilibrium at temperature T (either with ab initio dissipation or without it). Boltzmann’s classical equilibrium distributions generate, as Gaussian weight functions in momenta, orthogonal polynomials in momenta (the position-independent Hermite polynomialsHn’s). The moments...

2008
Karen Hallberg

The Density Matrix Renormalization Group (DMRG) has become a powerful numerical method that can be applied to low-dimensional strongly correlated fermionic and bosonic systems. It allows for a very precise calculation of static, dynamical and thermodynamical properties. Its field of applicability has now extended beyond Condensed Matter, and is successfully used in Statistical Mechanics and Hig...

Journal: :The journal of physical chemistry. A 2012
Jean Demaison Norman C Craig Emilio J Cocinero Jens-Uwe Grabow Alberto Lesarri Heinz Dieter Rudolph

N-Methylpiperidone (MPIP) and tropinone, which contain a structural motif found in numerous alkaloids, are too large to determine an accurate equilibrium structure either by ab initio methods or by experiment. However, the ground state rotational constants of the parent species and of all isotopologues with a substituted heavy atom ((13)C, (15)N, (18)O) are known from microwave spectroscopy. Th...

2011
Patrick Carlsson Tien Son Nguyen A. Gali J. Isoya N. Morishita T. Ohshima B. Magnusson

2001
A. J. van der Poorten Alf van der Poorten

The elementary nature and simplicity of the theory of continued fractions is mostly well disguised in the literature. This makes one reluctant to quote sources when making a remark on the subject and seems to necessitate redeveloping the theory ab initio. That had best be done succinctly. That is done here and allows the retrieval of some amusing results on pattern in the period of the continue...

2007
Jorge Marcelo Romero Soledad Bustillo Hugo Enrique Ramirez Maisuls Nelly Lidia Jorge Manuel Eduardo Gómez Vara Eduardo Alberto Castro Alicia H. Jubert

A thermochemical rather simple experimental technique is applied to determine the enthalpy of formation of Diperoxide of ciclohexanone. The study is complemented with suitable theoretical calculations at the semiempirical and ab initio levels. A particular satisfactory agreement between both ways is found for the ab initio calculation at the 6311G basis This set level. Some possible extensions ...

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