Benchmarking two-photon absorption with CC3 quadratic response theory, and comparison with density-functional response theory

We present a detailed study of the effects of electron correlation on two-photon absorption calculated by coupled cluster quadratic response theory. The hierarchy of coupled cluster models CCS, CC2, CCSD, and CC3 has been used to investigate the effects of electron correlation on the two-photon absorption cross sections of formaldehyde (CH2O), diacetylene (C4H2), and water (H2O). In particular, the effects of triple excitations on two-photon transition cross sections are determined for the first time. In addition, we present a detailed comparison of the coupled cluster results with those obtained from Hartree-Fock and density-functional response theories. We have investigated the local-density approximation, the pure Becke-Lee-Yang-Parr (BLYP) functional, the hybrid Becke-3-parameter-Lee-Yang-Parr (B3LYP), and the Coulomb-attenuated B3LYP (CAM-B3LYP) functionals. Our results show that the CAM-B3LYP functional, when used in conjuction with a one-particle basis-set containing diffuse functions, has much promise; however, care must still be exercised for diffuse Rydberg-type states.</p

Assisting Freshman Student-Athletes with Educational Planning and Career Development

In many academic support centers, a primary focus is on helping student athletes adjust to the collegiate environment and the increased demands of being a student and an athlete. This paper discussed the primary issues facing student-athletes with the interrelated career development issues, a description of a freshman academic and career exploration class, the results of the Survey of Career Development, and a discussion of intervention strategies and referral agencies. As a part of the Freshman Enrichment Program at Penn State University, all freshman student-athletes were enrolled in the Academic and Career Exploration course in spring semester 1988. The analysis was conducted only on the surveys completed by an individual in both the fall and spring semesters, forming a matched sample of 127 freshman student-athletes. A gender breakdown included 62 females and 65 males. This research found significant growth in career development from the fall semester to the spring semester for freshman student-athletes enrolled in an academic and career development course. The issue of student-athletes' lack of involvement and motivation in career planning and development presents developmental concerns to academic counselors

Recurrence relations for four-electron integrals over Gaussian basis functions

In the spirit of the Head-Gordon-Pople algorithm, we report vertical, transfer and horizontal recurrence relations for the efficient and accurate computation of four-electron integrals over Gaussian basis functions. Our recursive approach is a generalization of our algorithm for three-electron integrals [J.~Chem.~Theory Comput.~12, 1735 (2016)]. The RRs derived in the present study can be applied to a general class of multiplicative four-electron operators. In particular, we consider various types of four-electron integrals that may arise in explicitly-correlated F12 methods.Comment: 11 pages, 3 figures and 2 table

Excited States of Proton-bound DNA/RNA Base Homo-dimers: Pyrimidines

We are presenting the electronic photo fragment spectra of the protonated pyrimidine DNA bases homo-dimers. Only the thymine dimer exhibits a well structured vibrational progression, while protonated monomer shows broad vibrational bands. This shows that proton bonding can block some non radiative processes present in the monomer.Comment: We acknowledge the use of the computing facility cluster GMPCS of the LUMAT federation (FR LUMAT 2764

Self-Consistent Electron-Nucleus Cusp Correction for Molecular Orbitals

We describe a method for imposing the correct electron-nucleus (e-n) cusp in molecular orbitals expanded as a linear combination of (cuspless) Gaussian basis functions. Enforcing the e-n cusp in trial wave functions is an important asset in quantum Monte Carlo calculations as it significantly reduces the variance of the local energy during the Monte Carlo sampling. In the method presented here, the Gaussian basis set is augmented with a small number of Slater basis functions. Note that, unlike other e-n cusp correction schemes, the presence of the Slater function is not limited to the vicinity of the nuclei. Both the coefficients of these cuspless Gaussian and cusp-correcting Slater basis functions may be self-consistently optimized by diagonalization of an orbital-dependent effective Fock operator. Illustrative examples are reported for atoms (\ce{H}, \ce{He} and \ce{Ne}) as well as for a small molecular system (\ce{BeH2}). For the simple case of the \ce{He} atom, we observe that, with respect to the cuspless version, the variance is reduced by one order of magnitude by applying our cusp-corrected scheme.Comment: 23 pages, 5 figure

Festrede zum 50-jährigen Jubiläum des Marketing Clubs Bremen

Festrede zum 50-jährigen Jubiläum des Marketing Clubs Bremen1