Integral Programs Manual

Revision: 1.6 Date: 1997/08/14 14:14:00


Table of Contents


 
                                  PREFACE
                                  _______
 
    This   manual  describes  the  ATMOL  Gaussian  Integrals  program,  as
implemented on the Cyber-205 at UMRCC. This document is one in a series  of
twelve, supporting the ATMOL packages on the Cyber-205.
 
 
                               ATMOL MANUALS
                               _____________
 
 
                          1.   Introduction.
                          2.   Allocator.
                          3.   Gaussian Integrals.
                          4.   Gaussian Library.
                          5.   SCF.
                          6.   APSG.
                          7.   Transformation.
                          8.   Direct CI.
                          9.   Mulliken Analysis.
                         10.   Graphical Analysis.
                         11.   Property.
                         12.   Service.
 
 
 
                             TABLE OF CONTENTS
                             _________________
 
 
    1.   Introduction.                                               1
    2.   Program Specification.                                      1
    3.   The TITLE Directive.                                        2
    4.   The CONVERT Directive.                                      2
    5.   The NODISTANCE Directive.                                   2
    6.   The GEOMETRY Directive.                                     3
    7.   The GEOMGEN Directive.                                      4
    8.   GEOMETRY and GEOMGEN Directives in the same job.            9
    9.   The SYMCEN Directive.                                       9
   10.   The NOSYM Directive.                                        9
   11.   The COMBINE Directive.                                     10
   12.   The GTOS Directive.                                        10
   13.   Notes on the MERGE Option.                                 12
   14.   The EQUAL Directive.                                       12
   15.   The LIBRARY Directive.                                     12
   16.   The mixed use of the GTOS and LIBRARY Directives.          14
   17.   The ACCURACY Directive.                                    14
   18.   The IMIN Directive.                                        15
   19.   The IMAX Directive.                                        15
   20.   The MAINFILE Directive.                                    16
   21.   The DUMPFILE Directive.                                    16
   22.   The IBLOCK Directive.                                      17
   23.   The MAXBLOCK Directive.                                    17
   24.   The SIZE Directive.                                        18
   25.   The SAFETY Directive.                                      18
   26.   The ENTER Directive.                                       19
   27.   The RESTART Directive.                                     19
   28.   The RESTORE Directive.                                     20
   29.   Basic Directives for an Integral Job.                      21
   30.   Algorithms and Strategy of Integral Evaluation.            21
   31.   Error Monitoring.                                          23
   32.   Specimen Jobs.                                             25
   33.   References.                                                31
 
 

Introduction


    The ATMOL programs for the  computation  of  molecular  integrals  over
contracted  Gaussian  orbitals  is  outlined.  The  programs are capable of
evaluating set of integrals:
 
(a) Electron replusion integrals.
 
(b) Nuclear attraction integrals.
 
(c) Kinetic energy integrals.
 
(d) Overlap integrals.
 
(e) Dipole moment integrals.
 
The restrictions which the present  programs  place  on  the  user  are  as
follows:
 
(a) Maximum number of contracted orbitals = 255 for INTEGV.
 
(b) Maximum number of contracted orbitals = 255 for INTEGW.
 
(c) Maximum number of primitive functions within a contraction = 10.
 
(d) Functions of s, p and d may be used in the INTEGV module. By default
INTEGV uses Cartesian Gaussians. The directive COMBINE forces INTEGV to
use Sperical harmonic functions.
 
(e) Spherical  harmonic  functions of s, p, d, f, g, h and i may be used in
the INTEGW module.
 
(f) Maximum number of atoms = 100.
 

 

Program Specifications


 
    Data is accepted from FORTRAN stream 5, and consists of a  sequence  of
directives.  Printed  output  is  routed to FORTRAN stream 6. These streams
need not be explicitly mentioned in the JCL.
 
    The following data sets will be used by the  programs,  and  should  be
mentioned in the JCL, in REQUEST, ATTACH, MFLINK or GETFEP commands:
 
    MAIN  FILE:  This  dataset  contains  the  evaluated  2-electron atomic
integrals. In default mode this dataset is routed to the ATMOL stream  ED2.
This may be changed through the use of the MAIN FILE directive.
 
    DUMP  FILE: This dataset contains information on the geometry and basis
set of  the  system  under  investigation.  It  also  holds  the  evaluated
1-electron  atomic  integrals. The DUMP FILE is assigned in default mode to
ATMOL stream ED3. This can be changed through the  use  of  the  DUMP  FILE
directive.
 
    All pre-directives [1] are applicable and should  be  presented  before
the program specific directives described in the subsequent paragraphs. The
default memory requirement for the INTEGV program is such  that  it  should
always  be  allocated 3 large pages of main memory. For the INTEGW program,
the default memory at present has been  set  at  3  large  pages,  although
usually 1 or 2 large pages of main memory would surfice.
 
    In the following sections the data directives for INTEGV and INTEGW are
presented, with a brief explaination on how  they  can  be  used  and  what
purpose they serve.
 

The TITLE Directive

 
    The  TITLE  directive  allows  the  user to define up to a 80 character
title for a calculation. This directive extends over two  data  lines.  The
first  line contains the text TITLE in the first data field, the second the
required title.
 
   example:
 
       TITLE
       H2O CASE - INTEGRALS

 

The CONVERT Directive

 
    This  directive  may  be used to specify the units (Angstroms or Atomic
Units) which the user may wish to specify  the  Cartesian  co-ordinates  of
nuclei (see GEOMETRY or GEOMGEN directives) or symmetry centres (see SYMCEN
directive). The directive consists of a single data line read to  variables
TEXTA,TEXTB using format (2A).
 
    TEXTA   should be set to the character string CONVERT.
 
    TEXTB   can  be  set  to either ANGSTROM or AU. ANGSTROM means that the
input Cartesian co-ordinates will be assumed to be in Angstrom,  and  would
be  converted  to  atomic units by division by 0.529177. AU (or A.U.) means
the input co-ordinates will be assumed to be in atomic units.
 
    The CONVERT directive  may  be  omitted,  when  atomic  units  will  be
selected in default.

 

The NODISTANCE Directive

    This  directive  consists of a single data line, read to variable TEXT,
using A-format.
 
    TEXT    should be set to character string NODI.
 
    The NODI directive surpress the distance matrix and  must  precede  the
GEOMETRY or GEOMGEN directives.

 

The GEOMETRY Directive

 
    The GEOMETRY directive is used to define the  molecular  geometry.  The
first data line, the directive initiator, is read to variables TEXTA, TEXTB
using format (2A).
 
    TEXTA   should be set to the string GEOMETRY.
 
    TEXTB   may be set to one of the strings AU (or A.U.) or ANGSTROM,  and
is  used  to  define  the units in which the Cartesian co-ordinates will be
specified. If TEXTB is omitted,  the  units  will  be  as  specified  in  a
preceding CONVERT or GEOMGEN directive, or atomic units in default.
 
    The  last  line  of  the  GEOMETRY directive, the directive terminator,
consists of the text END in the first data field. Lines  appearing  between
the  initiator and terminator are the 'nucleus definition' lines. Each line
defines   a   given   nuclear   centre,   and   is   read   to    varaibles
X,Y,Z,CHARGE,TAG,TSTSYM using format (4F,2A).
 
    X,Y,Z   are  the  Cartesian  co-ordinates  of  the given centre, in the
appropriate units.
 
    CHARGE  is the charge of a given nucleus, the units being such that the
charge  of  the  proton is unity. Negative, zero and fractional charges are
allowed, as well as more usual postive integer values. It is also  possible
to  specify  the  text  DUMMY  instead  of  a  number centre for the CHARGE
parameter. In this case the centre will take no part in the calculation  of
molecular  integrals  (so  that  basis functions cannot be sited on a DUMMY
centre). DUMMY centres have been allowed  to  simplify  the  generation  of
molecular  geometries  when  using  the GEOMGEN directive, and for no other
purpose.
 
    TAG     is used to  give  the  centre  a  name  by  which  it  will  be
subsequently  known.  TAG  may  be  up to 8 characters long, and should not
include the 'space' character. If  the  m'th  nucleus  definition  line  is
presented  without  a  TAG  parameter, the system will supply the character
string representation of m (expressed as a decimal number) by default.
 
    TSTSYM  one of the strings SYSCEN,  CENSYM  or  SYM,  means  that  this
centre  will  be  used  as  a  'symmetry centre'. If TSTSYM is omitted, the
centre will not be used as a  'symmetry  centre'.  This  parameter  may  be
neglected  when  using  the  INTEGW program, since this module does not use
symmetry in the evaluation of the molecular integrals.
 
   example 1:
 
       GEOMETRY
       0 2.656347 0 1 H1
       -1.533643 0 0 1 H2
       1.533643 0 0 1 H3
       0 .885449 .719722 7 N
       END
 
 
   example 2:
 
       GEOMETRY
       0 2.656347 0 1
       -1.533643 0 0 1
       1.533643 0 0 1
       0 .885449 .719722 7
       END
 
 
    The difference between these two examples is the omission  of  the  TAG
parameters  in example 2. Thus centres which the user TAGged H1,H2,H3 and N
in example 1, are TAGged 1,2,3 and 4 respectively by the program in example
2.
 

The GEOMGEN Directive

 
    7.1  The  GEOMGEN  directive  may  also be used to define the molecular
geometry, either in  conjunction  with  the  GEOMETRY  directive  described
previously  or  alone. The first data line, the directive initator, is read
to varaibles TEXTA,TEXTB using format (2A).
 
    TEXTA   should be set to the string GEOMGEN.
 
    TEXTB   should be set to one of the strings AU (or A.U.)  or  ANGSTROM,
and is used to define the units in which the Cartesian co-ordinates will be
specified. If TEXTB is omitted,  the  units  will  be  as  specified  in  a
preceeding CONVERT or GEOMETRY directive, or atomic units in default.
 
    The  last  line  of  the  GEOMGEN  directive, the directive terminator,
consists of the text END  in  the  first  data  field.  Lines  between  the
directive  initator and terminator are of different 'types', each 'type' of
line being distinguished by the contents of the first data field. This data
field  is  always read in A format, and should contain one of the following
characters S,C,A or P.
 
    7.2 'S' type lines: Such lines are characterised by the  appearance  of
the  character S in the first data field, and are used to assign a floating
point value to a symbol. The second data field is also read in A format  to
SYMB,  and  should be set to the symbol whose value you wish to define. The
symbol can be up to 8 characters in length, and any EDCDIC  characters  are
allowed.  Successive  data  fields  are  read in pairs, using format (A,X).
Before proceeding further it is necessary to explain the format X, which is
non-standard,  and  used  only in the energy integrals program. When a data
field is read under format X, the field may contain either:
 
(a) A valid number as readable with format F.
 
(b) A symbol, whose value has been previously defined.
 
In both cases a REAL variable will be initialised. In case (a),  the  field
will be read in F format, and the REAL variable initialised accordingly. In
case (b), the REAL variable will be set equal  to  the  previously  defined
value of the symbol.
 
    At the time when the 'S' type line is read in, a REAL variable VALUE is
initialised  to zero. Each pair of (A,X) data fields is read and causes the
contents of VALUE to be altered according to the specification of OPER  and
the  value of GAMMA, as summarised in Table 1. When processing of all (A,X)
fields is complete,  the  enity  of  VALUE  can  subsequently  be  accessed
symbolically by SYMB.
 
                            Table 1
                            _______
    Interpretation of (A,X) pairs of data fields on 'S' type lines
    ______________________________________________________________
 
    OPER                            RESULT
    ____                            ______
 
      +                         VALUE = VALUE + GAMMA
      -                         VALUE = VALUE - GAMMA
      *                         VALUE = VALUE * GAMMA
      /                         VALUE = VALUE / GAMMA
   SQRT or +SQRT                VALUE = VALUE + DSQRT(GAMMA)
           -SQRT                VALUE = VALUE - DSQRT(GAMMA)
           *SQRT                VALUE = VALUE * DSQRT(GAMMA)
           /SQRT                VALUE = VALUE / DSQRT(GAMMA)
   SIN  or +SIN                 VALUE = VALUE + DSIN(GAMMA)
           -SIN                 VALUE = VALUE - DSIN(GAMMA)
           *SIN                 VALUE = VALUE * DSIN(GAMMA)
           /SIN                 VALUE = VALUE / DSIN(GAMMA)
   COS  or +COS                 VALUE = VALUE + DCOS(GAMMA)
           -COS                 VALUE = VALUE - DCOS(GAMMA)
           *COS                 VALUE = VALUE * DCOS(GAMMA)
           /COS                 VALUE = VALUE / DCOS(GAMMA)
   ASIN or +ASIN                VALUE = VALUE + DARSIN(GAMMA)
           -ASIN                VALUE = VALUE - DARSIN(GAMMA)
           *ASIN                VALUE = VALUE * DARSIN(GAMMA)
           /ASIN                VALUE = VALUE / DARSIN(GAMMA)
   ACOS or +ACOS                VALUE = VALUE + DARCOS(GAMMA)
           -ACOS                VALUE = VALUE - DARCOS(GAMMA)
           *ACOS                VALUE = VALUE * DARCOS(GAMMA)
           /ACOS                VALUE = VALUE / DARCOS(GAMMA)
 
The following supplementary notes on 'S' type lines may be helpful.
 
(a) If the symbol to be assigned a value is not one of S,C,A,P or END,
the line may be punched omitting the introductory S. For example,
the two data lines:
 
     S COSX COS 25.0
     COSX COS 25.0
 
are equivalent, both resulting in the symbol COSX  being  given  the  value
cos(25).
 
(b)  If  the  first operation is +, you may omit it. For example, the three
data lines:
 
     S SIGMA + 1.4
     S SIGMA 1.4
     SIGMA 1.4
 
all set the value to SIGMA to 1.4.
 
(c) The arguement for COS and SIN functions should be in degrees.
 
(d) The result from the ACOS and ASIN rountines will be in degrees, and  in
the range 0 to 180 (for ACOS) or -90 to 90 (for ASIN).
 
(e)  The  symbol  T is assigned the value 109.471220634491 (the tetrahedral
angle).
 
(f) The user may reset any symbol (including T) any number  of  times.  The
maximum number of symbols allowed is 100.
 
(g)  The user is permitted to set a symbol which takes the form of a number
readable in F format. If this number  appears  in  subsequent  data  fields
which  are  read  in X format, the symbolically ascribed value is used. The
sequence:
 
       S 1.9 1.8
       S F 1.9
 
will ascribe the value 1.8 to F.
 
   example 1:
 
The following sequence
 
       R 1.4
       ALPHA 30
       RX R *COS ALPHA
       RY R *SIN ALPHA
 
gives the values 1.4,  30,  1.4cos(30)  and  1.4sin(30)  to  the  variables
R,ALPHA,RX and RY respectively.
 
   example 2:
 
    It  is  required  to  compute the cos of half the tetrahedral angle and
place the result in X. The correct sequence is:
 
       X T / 2
       X COS X
 
The line
 
       X COS T / 2
 
will not do. The result would be X=COS(T)/2 rather than X=COS(T/2).
 
   example 3:
 
    It  is  required to assign the value 1.6 to equal the symbol S, and 1.3
to the symbol P. The following sequence is required:
 
       S S 1.6
       S P 1.3
 
Notice  that  the  introductory S is required for both these cases, as they
belong to the S,C,A,P and END group of symbols.
 
    7.3 'C' type lines: Such lines are characterised by the  appearence  of
the  character  C  in  the  first  data  field,  and are used to define the
Cartesian co-ordinates of a given centre in a  manner  closely  similar  to
that  employed  by  the  GEOMETRY  directive. The line is read to variables
TEXT,X,Y,Z,CHARGE,TAG,TSTSYM using format (A,4X,2A).
 
    TEXT    should be set to the character C.
 
    X,Y,Z   are the Cartesian co-ordinates of the centre, and these  fields
may  be  set  as  valid  floating  point  numbers,  or as previously defind
symbols.
 
    CHARGE  is  the  charge  of  the  given  nucleus   in   atomic   number
representation, and this field may be set as a floating point number, or as
a previously defined symbol. It is also possible to specify the text DUMMY,
and  in  this  case  the  centre  will  take  no part in the calculation of
molecular integrals. Notice that the centre will still be  declared  DUMMY,
even  if  the  user has assigned a value to the symbol DUMMY. DUMMY centres
have been allowed so as to permit simplification  of  molecular  geometries
when using 'A' type lines.
 
    TAG     is  used  to  give  the  centre  a  name  by  which  it will be
subsequently known. If the TAG parameter is omitted, and this is  the  m'th
centre  to  be  defined (including any centres defined in previous GEOMETRY
directives), TAG will be set as the decimal character string representation
of m by default.
 
    TSTSYM  one  of  the  strings  SYMCEN,  CENSYM  or SYM, means that this
centre will be used as a 'symmetry  centre'.  If  TSTSYM  is  omitted,  the
centre  will  not  be  used  as  a  symmetry  centre. This directive is not
applicable to the INTEGW program, since no  symmetry  is  employed  in  the
molecular integral evaluation.
 
    7.4  'P'  type lines: Such lines are characterised by the appearence of
the string P  in  the  first  data  field,  and  are  used  to  define  the
co-ordinates  of  the  present centre with respect to the co-ordinates of a
previously defined  centre.  The  line  is  read  to  varaibles  TEXT,TAGX,
AX,AY,AZ,CHARGE,TAG,TSTSYM using the format (5A,X,2A).
 
    TEXT     should be set to the character P.
 
    TAGX     should be set to the TAG of a previously defined centre, which
may have been declared DUMMY.
 
    AX,AY,AZ these A-fields may be set to  any  of  the  character  strings
X,Y,Z,-X,-Y  or  -Z.  Thus  if  AX is set to -Z, the 'x' co-ordinate of the
present centre will be set to minus  the  'z'  co-ordinate  of  the  centre
nominated by TAGX.
 
    CHARGE  see definition in 7.3.
 
    TAG     see definition in 7.3.
 
    TSTSYM  see definition in 7.3.
 
   example 1:
 
    The following data line
 
       P H1 -X Y Z 1 H2
 
defines the x, y and z co-ordinates of H2 to  be  equal  to  -x,  y  and  z
co-ordinates respectively of a previously defined centre, H1.
 
   example 2:
 
    The following data line
 
       P C1 -Y X -Z 6 C2
 
defines  the  x,y  and  z  co-ordinates  of  C2 to be equal to -y, x and -z
co-ordinates respectively of a previously defined centre, C1.
 
    7.5 'A' type lines: Such lines are characterised by the  appearence  of
the  character  A  in  the  first  data  field,  and are used to define the
co-ordinates of the present centre by defining bond lengths and angles with
respect  to three previously defined centres (some or all of which may have
been  declared  DUMMY).  The  line  is   read   to   varaibles   TEXT,TAGA,
TAGB,TAGC,R,THETA,ALPHA,CHARGE,TAG,TSTSYM using format (4A,4X,2A).
 
    TEXT    should be set to the character A.
 
    TAGA,TAGB,TAGC  should  be  set to the TAGs of three previously defined
centres, which will be referred as A,B and C. These centres should  not  be
                                                                    ___
collinear.
 
    R       should  be set equal to the bond length AD, where D will denote
the centre whose co-ordinates one wishes to define. R  may  be  defined  by
means of a symbol, or a floating point number, and will be assumed to be in
atomic units or Angstrom, according to the  user's  specifications  on  the
GEOMGEN, GEOMETRY or CONVERT directives.
 
    THETA   should  be  set equal to the DAB angle (in degrees), and should
be less than 180 degrees.
 
    ALPHA   should be set equal to the dihedral angle (in degrees) by which
one must rotate D about the A-B bond (in a clockwise direction) so that the
bonds AD and BC are eclipsed. The user should imagine looking down  the  AB
bond from A to B when performing this rotation.
 
    CHARGE  see definition in 7.3.
 
    TAG     see definition in 7.3.
 
    TSTSYM  see definition in 7.3.
 


GEOMETRY and GEOMGEN directives in the same job

 
    The appearance of  both  directives  in  the  same  input  document  is
allowed, the effect being to append the data within the second directive to
that of the first. The multiple appearance  of  the  GEOMETRY  and  GEOMGEN
directives  (or  both)  is  also allowed, the centres defined by successive
directives being appended to the list.

 

The SYMGEN Directive

 
    The SYMCEN directive consists of  one  data  line,  read  to  varaibles
TEXT,X,Y,Z using format (A,3X).
 
    TEXT    should be set to one of the character strings SYSCEN, CENSYM or
SYM.
 
    X,Y,Z   defines the Cartesian co-ordinates of a point to be used by the
program as a 'symmetry centre'. These parameters may be set either with the
use of symbols defined in a previous GEOMGEN  directive,  or  by  means  of
standard F format. The units of distance will be as specified in a previous
GEOMETRY, GEOMGEN or CONVERT directive, or atomic units in default.
 
    The program will consider symmetry operations (such as rotations by  90
or 180 degrees about the x,y,z axis passing through the symmetry centre) in
order to classify any 2-electron integrals which may be of equal value,  or
equal  in  absolute value but of opposite sign, so as to produce savings in
computer time  by  the  elimination  of  redundant  computation  when  such
integrals are evaluated. The user is asked to note the following points:
 
(a) The  program will automatically use the centre of charge of the nuclear
framework as a symmetry centre.
 
(b) A maximum of eleven symmetry centres  can  be  declared  by  the  user.
Greater than eleven of such centres will be discarded.
 
(c) To  maximise  the use of molecular symmetry, orient the molecule within
the co-ordinate system so as to maximise the number of 2-electron integrals
which are zero by symmetry.
 
(d) The  centre  of charge of nuclear framework is often adequate to define
all useful symmetry operations of the molecule. However,  it  is  sometimes
the  case  that  a  fragment  of the molecule can be identified having high
local symmetry. The SYMCEN directive should be used to define the  symmetry
centre of such fragments.
 
    It  should  be  noted  that  the  SYSCEN directive is not valid for the
INTEGW program, since no symmetry is employed  in  the  molecular  integral
evaluation.

 

The NOSYM Directive

 
    The  NOSYM directive, if used, causes the program to evaluate molecular
integrals without using algorithms designed to improve efficiency by  means
of molecular symmetry. The directive consists of a single data  line,  with
the text NOSYM in the first data field.
 
    It  is  not  recommend the user to enforce this directive, since it was
designed to permit the evaluation  of  the  efficiency  of  the  'symmetry'
algorithms.

 

The COMBINE Directive

 
    The  COMBINE  directive  consists  of a single data line, with the text
COMBINE in the first data field. If used, the directives causes D groups of
basis  functions  to  be  constructed  in 'spherical harmonic' form. If the
COMBINE directive is omitted, the D group of  basis  function  will  be  in
standard 'Cartesian' form.
 
    The  COMBINE  directive does not apply to the INTEGW program since this
program evaluates the molecular integrals in terms of 'spherical  harmonic'
functions.  Invoking  the COMBINE directive when using INTEGW, will produce
an error status.

 

The GTOS Directive

 
    12.1 The GTOS directive provides one method of defining the basis  set.
The  first  line, the directive initiator, consists of the character string
GTOS or GAUSSIAN in the first data field. The last line of  the  directive,
the directive terminator, consists of the text END in the first data field.
Lines between the initiator  and  terminator  define  the  basis  set,  and
consist  of  'group  definition' and 'primitive definition' lines. The data
for each group of contracted functions is introduced in turn, as follows:
 
(a) The group definition line is read to varaibles TYPE,TAGA,INFORM,  MERGE
using (2A,I,A).
 
    TYPE    should  be  set to one of the characters S,P,D,F,G,H or I, only
S,P and D are valid when using INTEGV. These symbols defines  the  type  of
group of basis functions being introduced.
 
    TAGA    should  be  set  to  a  TAG  of one of the centres (not a DUMMY
centre) defined in a GEOMETRY or GEOMGEN  directive.  The  group  of  basis
functions will be sited on the nominated centre.
 
    INFORM= 0  the contractions are to be normalised.
          =-1  the contractions are to be left unnormalised.
          =999 the  normalisation  procedure used, and the orbital exponent
and contraction coefficients of the primitives are to be  as  selected  for
the preceding group of basis functions in the data stream.
 
    MERGE   consists of a three character code word.
 
 MERGE=NEW:the  group  of  basis  functions  has not appeared in a previous
reference calculation.
 
 MERGE=OLD:the  group  of  basis  functions  has  appeared  in  a  previous
reference calaculation
 
    The MERGE parameter may be omitted, when it is given the default  value
NEW. In this case, INFORM may also be omitted, the default value of 0 being
used for the latter.
 
(b) The primitive definition lines follow the group  definition  line,  and
are  used  to  define the contraction coefficients and orbital exponents of
the primitive associated with the group. If NTERM primitives are to be used
(NTERM<11),  NTERM  primitive  definition  lines are required, each read to
CTRAN,ZETA using format (2F).
 
    CTRAN    the contraction coefficient of the primitive.
 
    ZETA     the orbital exponent of the primitive.
 
    12.2 The following example defines a poor basis set  for  Ammonia,  the
centre TAGging conventions being used are the example given in the GEOMETRY
directive.
 
    GTOS
    S H1
    0.18 10.25
    0.86 2.346
    S H2 999
    S H3 999
    S H1
    1.0 0.255
    S H2 999
    S H3 999
    S N
    0.16 3474.0
    0.24 216.6
    S N
    0.8 68.48
    0.61 8.566
    S N
    1.0 0.906
    P H1
    1.0 0.1
    P H2 999
    P H3 999
    P N
    0.22 13.95
    0.43 1.598
    P N
    1.0 0.2609
    END
 
 
    12.3 Note that there is no restriction as to the ordering of the groups
in  the  input  stream. However the program will internally re-organise the
data to produce a list of ordered functions. A copy of  the  orginal  list,
together with the re-ordered list is printed.
 
 

Notes on the MERGE Option

 
    The MERGE parameter, which appears in the group definition lines of the
GTOS  directive,  has  been  implemented  so  that the 2-electron integrals
computed in a previous reference  calculation  which  are  in  common  with
integrals  required  in  the  current  calculation  are not recomputed, but
re-used.
 
    In the current calculation, the integrals program computes and  outputs
to  the  MAIN  FILE  all  2-electron integrals not common with any of those
available from the reference calculation. Such integrals are  characterised
by  the  fact at least one basis function involved in the integral has been
declared NEW in the current calculation. This MAIN FILE produces a  NEWFILE
mainfile.
 
    The  ATMOL  SERVICE  program  [2] is used to isolate from the MAIN FILE
produced in the reference calculation those integrals which are  common  to
both  calculations. That is, those integrals where all four basis functions
are declared OLD in the current calculation. The SERVICE program produces a
file  which  will be called the MERGEFILE. The NEWFILE and MERGEFILE, which
between  them  contain  all  the  necessary  integrals  for   the   current
calculation, may now be passed on to the SCF program for processing.
 
    Basis  functions  are  deleted by simply removing all reference to such
functions from the input data for the current calculations.
 
    The user should note that a MERGE strategy  is  not  employed  for  the
1-electron integrals, these being computed afresh for each case.

 

The EQUAL Directive

 
    This  directive  consists of a single data line, which may be repeated,
and is read to variable TEXT,nTAG using format (A,nA).
 
    TEXT    should be set to the character string EQUAL.
 
    nTAG    should be set to the  TAG  centres  (see  GEOMETRY  or  GEOMGEN
directives).  The  first  TAG  centre  is the defining basis centre and the
remainder of the TAGged parameters are equilvalenced with that set of basis
functions.
 
    example :
 
       EQUAL H1 H2 H3 H4
 
    The  TAGged  labels  H2,H3,H4 are equated with the H1 TAGged label. The
use of the EQUAL directive may be used instead of  the  GTOS  subdirective,
INFORM=999. Mixing of EQUAL and INFORM=999 is permitted.

 

The MOLECULE Directive

The molecule directive is meant as a tool for counterpoise calculations. The counterpoise approach is the way to calculate Basis Set Superposition Error (BSSE) free interaction energies. To calculate the interaction energy of 2 molecules one calculates the energy of the supermolecule system and of each molecule in the total basisset of the 2 molecules. The interaction energy is the difference between the supermolecule energy and the molecule energies. The 3 energy calculations differ only in the 1-electron integrals.

The molecule directive offers a means to specify which nuclei make up a molecule and the section number where the 1-electron integrals for that molecule (in the total basis) will be stored. The syntax of the molecule directive is:

    MOLECULE ISMOL
      MOLA ISECA ATMA1 [ ATMA2  ATMA3 .. ]
    [ MOLB ISECB ATMB1 [ ATMB2  ATMB3 .. ]  ]
    END
where
MOLECULE
This is a literal string selecting the molecule directive.
ISMOL
This is an integer specifying the section number where the 1-electron integrals will be stored for the complete supermolecule. This supermolecule contains all nuclei specified in the geometry.
MOLA, MOLB, ..
These are strings specifying the names of the molecules A, B, .. respectively. Note that only the first 8 characters are used.
ISECA, ISECB, ..
These are integers specifying the section number where the 1-electron integrals for the molecules A, B, .. will be stored.
ATMA1, ATMA2, ATMA3, ..
This is a line of strings specifying the names of the atoms that make up the molecule A. The names of the atoms should be in accordance with the names specified in the GEOMETRY or GEOMGEN directive. Note that only the first 8 characters are used. The string may be extended to the next line specifying the literal strings PTO or ZOZ.
END
This is a literal string indicating the end of the MOLECULE directive.
Note that the molecule directive is restricted to a maximum of 10 molecules and a maximum of 200 atoms totally.

For a counterpoise calculation on a O2 - H2O supermolecule the following molecule directive may be specified,

     Example:

       MOLECULE 50
         H2O  51  H1 H2 O3
         O2   52  O1 O2
       END
This results in: