Strongly orthogonal geminal

The earliest such attempts go back to 1953, when strongly orthogonal antisymmetrized geminal products (SOAGP) were employed [1, 2]. A strongly orthogonal geminal is such that Jgi(l,2)g2(2,3)d2 = 0, while the weaker... 

Recently, an alternative scheme based on singlet-type strongly orthogonal geminals (SSG) was proposed [5]. In this scheme, the wavefunction is split into gem-inal subspaces depending on the number of spin-up or spin-down electrons, n and n, respectively, while the wavefunction is filled up with one Slater determinant. 

The antisymmetrized product of strongly orthogonal geminals is denoted by the acronym APSG. Properties of this wave function, its construction and use, will be discussed in the forthcoming sections. 

The importance of this statement cannot be over-emphasized. Strongly orthogonal geminal expansions in mutually exclusive subspaces can be done without any loss of generality provided one determines these subspaces which, for brevity, will be called Arai-subspaces hereinafter. 

Kapuy E (1967) The Physical Society of Japan (eds). Applicability of almost strongly orthogonal geminals in many-electron wave function. Series in Selected Papers in Physics, Theory of Molecular Structure II... 

Keywords Density matrices, Wigner solid, strongly orthogonal geminals... 

Low-Order Density Matrices Built from Strongly Orthogonal Geminals... 

Since our wave function is most conveniently written in the form (69), i.e. as an antisymmetrized product of strongly orthogonal geminals i), the name APSG is now commonly used for this ansatz. 

The separated electron pair concept, which was first proposed by Hurley et al. [14] and which was later referred to as antisymmetrized product of strongly orthogonal geminals (APSG) [15], is also a special case of the group function concept. This kind of wave function is qualitatively correct at all internuclear distances and it can be improved either perturbationally [16, 17] or variationally [18]. 

The first pair theory was proposed as long ago as 1953 the antisymmetrized product of strongly orthogonal geminals (APSG) of Hurley et a ... 

The perturbation theory has widely been used in quantum chemistry to account for the dynamical electron correlation in single Slater [i.e., Hartree-Fock (HF)] and multideter-minantal states [1]. Suijdn has woiked on the perturbation theories for both HF and non-HF references. For non-HF reference functions, he and his cowoikers proposed a series of multiconfiguration perturbation (MCPT) theories [2-6]. Because the MCPT theories are applicable to any reference functions, they have occasionally been applied to the antisymmetric product of strongly orthogonal geminals wave functions [7-9]. 

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