Gaussian 03 Online ManualLast update: 2 October 2006 | |

This page outlines the various size limitations that exist
within ## Z-matrix LimitationsThere are restrictions on the size of a Z-matrix, the maximum
number of variables and the maximum number of atoms within a calculation. These
are set consistently for a maximum of 20000 real atoms (including ghost but not
dummy atoms), and a maximum of 20000 Z-matrix centers (atoms, ghost atoms, and
dummy atoms). In addition, the maximum number of variables that can be specified
in an optimization is unlimited for Berny optimizations but must not exceed 50
for Murtaugh-Sargent or ## Basis Set LimitationsThroughout the ## Integral Program LimitationsTo understand fully the limitations in the integral
programs, the reader must have some understanding of the concepts presented in
discussion of the The other major restriction that appears in the integral
programs is in the manner in which integral labels are packed. These limits apply
only when two-electron integrals are written out and can be avoided entirely by
using When the conventional integral storage
procedure is selected (in contrast to the Raffenetti ("PK") storage modes [574]),
the suffixes μ, ν, λ, and σ of the two-electron integral (μν|λσ)
are packed into a computer word as 8-bit quantities in the UNIX version, and as
16-bit quantities in the UniCOS version. This in effect limits the number of basis
functions to 255 under UNIX for conventional calculations in this mode. When the
Raffenetti modes are selected (for ## SCF and Post-SCF LimitationsThere are only a few other links which have additional dimensioning limits. There is no further restriction for RHF, UHF, ROHF, DFT, MP, CI, QCISD, CC, or BD calculations using the default algorithms. Complex HF calculations are limited to 180 basis functions, and complex MP2 calculations are effectively limited by a requirement of O(N3) words of main memory, and are also limited to f functions. The GVB program is limited to 100 paired orbitals, which is not a restriction in practice. The
remaining restrictions are in some of alternative programs which must be specifically
requested. ## NBO DimensionsNBO is dimensioned for 200 atoms and 10000 basis functions. |