1SCF input parameters
2
3Convergence threshold
4
5    THRESH tol
6
7    The convergence criterion is on the maximum value of the gradient
8    vector.  The default value is 10^-6.
9
10
11Maximum number of iterations
12
13    MAXITER n
14
15    default is 5 ... usually only 3 are needed.
16
17    e.g.
18
19        maxiter 10
20
21
22Input/output MO vectors
23
24    VECTORS [input] <atomic|hcore|filename> [output <filename>]
25
26     output vectors default to either the same filename as the
27     input vectors if they were read from a file or to the
28     filename movecs (which is searched for by the application).
29
30     E.g.
31
32     These two are equivalent and implement the default
33
34         vectors atomic output movecs
35
36         vectors input atomic output movecs
37
38     This gets input vectors from one file and outputs final
39     vectors back to the same file
40
41         vectors h2o.movecs
42
43     This gets input vectors from one file and outputs final
44     vectors to another file
45
46        vectors input h2o.guess output h2o.final
47
48
49
50SCF level shifting
51
52    LEVEL [pcg initial [tol final]] [nr initial [tol final]]
53
54    Both the 1-electron preconditioned conjgugate gradient (PCG) and
55    the Newton-Raphson (NR) use level shifting to stabilize convergence
56    (by making the preconditioning matices more positive definite and
57    diagonally dominate).  For both you can specify an initial level
58    shift, a gradient value at which to change shifts, and a final
59    level shift.  The defaults
60
61       pcg initial = 10.0
62       pcg change shift at max. gradient = 0.5
63       pcg final = 0.0
64       nr  initial = 10.0
65       nr  change shift at max. gradient = 0.5
66       nr  final = 0.0
67
68    are almost always acceptable because the program will increase
69    the level shift if convergence problems are encountered with the
70    preconditioning.  However, some cases do require increased level
71    shifts to speed convergence
72
73    e.g.
74
75      This enables the default options
76
77      level nr 0 0 0 pcg 10 .5 0
78
79
80Controlling use of newton-raphson quadratically convergent algorithm
81
82    NR tol
83
84    The QC algorithm (use of exact hessian preconditioner) is enabled
85    by default when the maximum element of the orbital gradient falls
86    below 0.1.  This value can be changed using this directive
87
88    e.g.
89
90       This enables the default
91
92       NR 0.1
93
94       This disables the QCSCF entirely
95
96       NR 0.0
97
98
99Atomic guess shift (subject to change)
100
101     SET "scf:atom shift" real value
102
103     The atomic guess routines form a density matrix (D) from a superposition
104     of the atomic density matrices.  Vectors are obtained from diagonalizing
105     the matrix
106
107        Fock(D) - shift * SDS
108
109     If the density matrix was idempotent then this is equivalent to
110     standard level shifting.  The default value of shift is 0.0 which seems
111     best for 'normal' molecules.  Values of 1-2 can help with transition metals.
112     There is no special input for this parameter so U have to use the generic
113     set directive.
114
115