As shipped, deMon2k has some preset limits for memory and disk space requirements, number of atoms, and number of basis and auxiliary functions. Table 1 summarizes those as-shipped limits.

Table 1: Parameter settings in deMon2k as shipped.
Parameter Setting Description
MAXDISK 51200 Maximum disk size for scratch files in Mbytes
MAXRAM 2048 Maximum RAM size for program kernel in Mbytes
PRORAM 256 RAM size reserved for program data in Mbytes
MAXATMM 15000 Maximum number of MM atoms
MAXATOM 1000 Maximum number of QM atoms
MAXAUX 20000 Maximum number of auxiliary functions
MAXAUXSET 10000 Maximum number of auxiliary function sets
MAXAUXSHL 10000 Maximum number of auxiliary function shells
MAXCON 21 Maximum degree of contraction
MAXCUBE 500000 Maximum number of (cube) embedding points
MAXECPGTO 10000 Maximum number of ECP Gaussian functions
MAXECPSHL 3000 Maximum number of ECP shells
MAXGTO 20000 Maximum number of primitive Gaussian functions
MAXLAUX 6 Maximum L quantum number for auxiliary functions
MAXLBAS 6 Maximum L quantum number for basis functions
MAXLECP 5 Maximum L quantum number for ECP functions
MAXLINK 4 Maximum number of molecular mechanics links
MAXLMCP 3 Maximum L quantum number for MCP functions
MAXLSUM 8 Maximum L quantum number for double asymptotic ERIs
MAXMCPGTO 10000 Maximum number of MCP Gaussian functions
MAXMCPSHL 3000 Maximum number of MCP shells
MAXMCPSTO 6000 Maximum number of contracted MCP (STO) orbitals
MAXPAT 10 Maximum number of geometry pattern
MAXSHL 5000 Maximum number of (STO) orbital shells
MAXSTO 10000 Maximum number of contracted (STO) orbitals
MAXTBSTO 10000 Maximum number of tight-binding (STO) orbitals

These limits are specified in the section user defined parameters of the parameter.h file. If a calculation violates these limits, the program stops and prints PARAMETER EXCEEDED statement(s) for the parameters that must be changed. In this case, please change only the first parameter listed as exceeded to the suggested (USED) value and recompile the program (the following ones may be corrupted by array boundary violations). Repeat this procedure until all PARAMETER EXCEEDED statements disappear. We recommend that you not increase the MAXRAM value over the physical memory (RAM) available. Doing otherwise may result in large paging overhead during program execution. Remember also that the size for MAXRAM is given in MB/Core, i.e. the total amount of RAM assumed available for the program in case of a parallel execution equals MAXRAM $\times$ number of cores.

In the case of a conventional SCF calculation, disk requirements are dominated by the size of the electron repulsion integral scratch file ioeri.scr. In the case of a direct SCF (see 4.5.1) calculation, the files ioscf.scr, iocdf.scr, and iogrd.scr dominate. The files 4GBYTE.H and 6GBYTE.H contain alternative parameter settings for larger deMon2k versions with up to 1000 and 2000 atoms, respectively. If one of these settings is to be used, copy the corresponding file to parameter.h.