This file is indexed.

/usr/share/psi/samples/frac/input.dat is in psi4-data 1:0.3-5.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
#! Carbon/UHF Fractionally-Occupied SCF Test Case 

# References
reference_energies = {\
    5.500E+00 : -3.7479827870463325E+01,\
    5.600E+00 : -3.7519777157724391E+01,\
    5.700E+00 : -3.7560494710854833E+01,\
    5.800E+00 : -3.7602027729245712E+01,\
    5.900E+00 : -3.7644429418258895E+01,\
    6.000E+00 : -3.7687760545777166E+01,\
    6.100E+00 : -3.7686231278907293E+01,\
    6.200E+00 : -3.7685148131020334E+01,\
    6.300E+00 : -3.7684578391807577E+01,\
    6.400E+00 : -3.7684604177989534E+01,\
    6.500E+00 : -3.7685326293326547E+01,\
    6.600E+00 : -3.7686869113983775E+01,\
    6.700E+00 : -3.7689386736023820E+01,\
    6.800E+00 : -3.7693070640744025E+01,\
    6.900E+00 : -3.7698159082829754E+01,\
    7.000E+00 : -3.7704948149321964E+01,\
}

# => Cation Computation (Doublet) <= #

# Specify molecule
molecule {
1 2         # Starting from the cation 
C           # Single C in Z-mat (also takes xyz)
symmetry c1 # C1 is best, otherwise the occupation gets squirrely
}

# Standard SCF options (this one is DF-UHF)
set print 2                  # Higher print level for extra properties
set basis aug-cc-pvdz        # Primary basis
set scf_type df              # SCF algorithm is DF
set reference uhf            # Reference is UHF

# N-1-electron SCF
Em1 = energy('scf')

# => Anion Computation (Quartet) <= #

# Specify molecule
molecule {
-1 4        # Starting from the anion 
C           # Single C in Z-mat (also takes xyz)
symmetry c1 # C1 is best, otherwise the occupation gets squirrely
}

# Standard SCF options (this one is DF-UHF)
set print 2                  # Higher print level for extra properties
set basis aug-cc-pvdz        # Primary basis
set scf_type df              # SCF algorithm is DF
set reference uhf            # Reference is UHF
set d_convergence 7          # 8 digits seems unstable

# N+1-electron SCF
Ep1 = energy('scf')

# => Neutral and cationic FO-UHF (Starting from the Neutral) <= #

# Specify molecule
molecule {
0 3         # Starting from the neutral
C           # Single C in Z-mat (also takes xyz)
symmetry c1 # C1 is best, otherwise the occupation gets squirrely
}

# Standard SCF options (this one is DF-UHF)
set print 2                  # Higher print level for extra properties
set basis aug-cc-pvdz        # Primary basis
set scf_type df              # SCF algorithm is DF
set reference uhf            # Reference is UHF

# N-electron SCF
E0 = energy('scf')

# Lists of occupation numbers 
low_occs  = [0.5, 0.6, 0.7, 0.8, 0.9]
high_occs = [0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0]

# Initialize the result lists
occs = []
energies = []

# Do partially occupied HOMO
for occ in low_occs:

    # New options for FRAC
    set frac_start 3
    set mom_start 4
    set frac_occ [4]
    set frac_val [$occ]
    
    # Frac SCF
    En = energy('scf')
    
    # Append results
    occs.append(5.0 + occ)
    energies.append(En)

# Append the neutral species result
occs.append(6.0)
energies.append(E0) 

# => Anionic FO-UHF (Starting from the Anion) <= #

# Specify molecule
molecule {
-1 4        # Starting from the anion 
C           # Single C in Z-mat (also takes xyz)
symmetry c1 # C1 is best, otherwise the occupation gets squirrely
}

# Standard SCF options (this one is DF-UHF)
set print 2                  # Higher print level for extra properties
set basis aug-cc-pvdz        # Primary basis
set scf_type df              # SCF algorithm is DF
set reference uhf            # Reference is UHF
set d_convergence 7          # 8 digits seems unstable

# Do partially occupied LUMO
for occ in high_occs:

    # New options for FRAC
    set frac_start 7
    set mom_start 9
    set frac_occ [5]
    set frac_val [$occ]
    
    # Frac SCF
    En = energy('scf')
    
    # Append results
    occs.append(6.0 + occ)
    energies.append(En)

# Print the results out
print_out('\n    ==> Fractional Occupation Traverse Results <==\n\n')

print_out('\tCation  Energy = %24.16E\n' % Em1)
print_out('\tNeutral Energy = %24.16E\n' % E0)
print_out('\tAnion   Energy = %24.16E\n\n' % Ep1)

print_out('\t%-8s %-24s\n' %('Nelec', 'Energy'))
for k in range(len(occs)):
    print_out('\t%8.3E %24.16E\n' % (occs[k], energies[k]))

# Test the results 
for k in range(len(occs)):
    compare_values(reference_energies[occs[k]], energies[k], 8, "%11.3E electron energy" % occs[k])