The hess Section of the Jaguar Input File

If an input file has a non-empty hess section, the keyword inhess in the gen section is set to 2 automatically, and a Hessian is read in from the hess section. Since for a Hessian H, Hij = Hji, only the elements with ji are read in, and the program symmetrizes the matrix itself later.

Since the Hessian has dimensions of 3N×3N, where N is the number of atoms (including dummy atoms), it may be large, so files listing all elements in each row by order of rows could be unwieldy and difficult to read. Therefore, the Hessian is assumed to be presented in blocks composed of five columns each (with the last block possibly having fewer than five columns, if 3N is not a multiple of five). The format used for the hess section is the same as that used in Gaussian files or BIOGRAF (.hes) files. All Hessian elements for dummy atoms should be set to 0 (as they are in Jaguar output).

Each set of elements from a block of five columns should be preceded by a line containing one or more arbitrary integer labels; for instance, column labels could be convenient for keeping track of the elements when looking at the hess section. All of the elements within a five-column block for which j (the column indicator) is less than or equal to i (the row indicator) are then read in, one row at a time. Each row of five or fewer matrix elements starts with an arbitrary integer label; this integer is not used in the program, but can be used to label the row, for example. When the relevant matrix elements from that entire five-column block have been read in, the next block is read in the same way, until all of the matrix elements for the lower triangle of the matrix have been entered.

For example, in the unlikely event that you wanted to enter this Hessian:

11

21

31

41

51

61

71

81

21

22

32

42

52

62

72

82

31

32

33

43

53

63

73

83

41

42

43

44

54

64

74

84

51

52

53

54

55

65

75

85

61

62

63

64

65

66

76

86

71

72

73

74

75

76

77

87

81

82

83

84

85

86

87

88

you would need to enter the elements from the bottom triangle of the Hessian (shown in bold above) in the following way:

&hess
1
1     11
2     21     22     
3     31     32     33     
4     41     42     43     44     
5     51     52     53     54     55     
6     61     62     63     64     65     
7     71     72     73     74     75     
8     81     82     83     84     85     
6
6     66     
7     76     77     
8     86     87     88     
&

Here the beginning of a block is marked with the index of the first column of the Hessian, and the rows in the block have the row number as the first value. This practice helps you to identify the Hessian matrix elements, though as mentioned above, you can have arbitrary integer values in the label (first) column of the input.

Geometry Optimization Examples

Transition State Geometry Optimization Examples