Ab Initio Quantum Chemistry Programs

This section surveys some of the available ab initio quantum chemistry program packages. 

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The method presented here allows, starting with trial gaussian functions, a partial analytical treatment which we have used to improve the LCAO-GTO orbitals (trial functions) essentially obtained from all ab initio quantum chemistry programs. As in r-representation, trial functions (t>i( Hp) (Eq. 21) are conveniently expressed as linear combinations of m functions Xi(P) themselves written as linear combinations of Gt gaussian functions (LCAO-GTO approximation) gta(P). 

T. Yanai, H. Nakano, T. Nakajima, S. Hirata, T. Tsuneda, Y. Kawashima, Y. Nakao, M. Kamiya, H. Sekino, and K. Hirao, UTCHEM—a program for ab initio quantum chemistry, in Lecture Notes in Computer Science, Springer-Verlag, Berlin, 2003. 

Because of the latter computational difficulties, another choice of basis sets has been preferred, mainly by the ab initio quantum-chemistry community, and this basis set has actually given an important computer program its name. According to Boys [59], a Gaussian-type orbital (GTO) may also serve as a basis function, and the radial-dependent part scales as... 

As part of the education for graduate students, ETH Zurich, like many other European universities, does not offer a graduate school , but advanced lectures in molecular dynamics and molecular simulation (W. F. van Gunsteren), and numerical quantum chemistry (T. K. Ha, H. P. LUthi) are offered. In these courses the modern methods in molecular dynamics and ab initio quantum chemistry are addressed and discussed based on examples from the current research literature. These lectures are also part of the ETH Computational Science and Engineering curriculum, a program which offers a degree based on an education with an interdisciplinary character (chemistry, physics, biology, mathematics, and computer science see http //www.inf.ethz.ch/departinent/WR/RW/). 

With quantum-mechanical methods, the second derivatives of the energy could be used directly for the FF and atomic polar tensors (APT) for the dipole derivatives. Both are standardly computed in most quantum-chemistry programs but for accurate results, moderately large basis sets and/or some accommodation for correlation interaction is needed. Until recently, this has restricted most ab initio studies to modest-sized molecules. 

Computer programs for the HMO, EH, PPP, CNDO, INDO, MINDO, and ab initio SCF MO methods can be obtained from the Quantum Chemistry Program Exchange, Chemistry Department, Indiana University, Bloomington, Indiana, 47401. 

The first commercially available quantum chemistry program capable of analyzing large structures in practical amounts of time. For ab initio (including high-level correlated methods) and DFT. Q-Chem is available for PCs running under LINUX or Windows, for UNIX workstations, and for supercomputers. 

The conductor-like continuum solvation model, modified for ab initio in the quantum-chemistry program GAMESS, implemented at the Meller-Plesset order 2 (MP2) level of theory, has been applied to a group of push-pull thiophene systems to illustrate the effects of donor/acceptor and solvation on the stability and energetics of such systems. The most accurate theoretical gas- and solution-phase data to date have been presented for the parent thiophene-2-carbaldehyde system <2000JCP(113)7519>. 

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