CASTEP file formats - TDDFT
The .tddft
file contains detailed information about the results of a CASTEP calculation of excitations in the time-dependent DFT approach.
The header contains information about the structure, this block is followed by the representation of excited states as a superposition of Kohn-Sham one-electron bands. The overlap between occupied and unoccupied states gives a useful indication of the degree of charge transfer in every given excitation (if the value is significantly lower than 1.0, the TD-DFT description might be inaccurate since it does not take charge transfer into account).
The final section contains spectroscopic data; excitations energy, singlet or triplet character, level of convergence, and transition dipoles (the position operator between the ground-state wavefunction and the first order response wavefunction for the Nth excited state from TDDFT, ). The transition dipole is projected onto the Cartesian axes. The character can be marked as "spurious" to reflect the fact that there are mathematically valid solutions to the linear-response TDDFT eigenvalue problem that are not physical (Heßelmann and Görling, 2009). These are solutions that provide a pure Kohn-Sham orbital transition, with no contribution from the exchange-correlation action. In terms of observables, the matrix elements will be zero (numerically so for computed quantities), and therefore harmless unless you want to select a specific state, for example for a structure optimization.
The file has the following format:
BEGIN header CASTEP generated TDDFT output Highest occupied band for spin channel 1 4 Highest occupied band for spin channel 2 4 Energies in eV Unit cell vectors (A) 2.087121 0.737909 1.278096 0.000000 2.213726 1.278096 0.000000 0.000000 2.556191 Fractional Co-ordinates B 1 0.375000 0.375000 0.375000 N 2 0.625000 0.625000 0.625000 END header BEGIN Characterisation of states as Kohn-Sham bands State Occ. Unocc. Overlap 1 3 --> 6 0.497606 1 3 --> 7 0.002308 1 4 --> 6 0.002307 1 4 --> 7 0.497591 Total overlap for state 1 = 0.996985 2 2 --> 6 0.494925 2 2 --> 7 0.003908 2 3 --> 5 0.012166 2 4 --> 5 0.488863 Total overlap for state 2 = 0.999931 3 2 --> 6 0.003907 3 2 --> 7 0.494894 3 3 --> 5 0.488844 3 4 --> 5 0.012162 Total overlap for state 3 = 0.999930 4 2 --> 6 0.055707 4 2 --> 7 0.104554 4 3 --> 5 0.097408 4 3 --> 6 0.155035 4 3 --> 7 0.169678 4 3 --> 8 0.022879 4 4 --> 5 0.061031 4 4 --> 6 0.164557 4 4 --> 7 0.153354 4 4 --> 8 0.013906 Total overlap for state 4 = 0.999524 5 2 --> 6 0.104116 5 2 --> 7 0.055983 5 3 --> 5 0.059369 5 3 --> 6 0.166594 5 3 --> 7 0.147638 5 3 --> 8 0.013905 5 4 --> 5 0.100521 5 4 --> 6 0.161928 5 4 --> 7 0.164886 5 4 --> 8 0.022856 Total overlap for state 5 = 0.999524 6 2 --> 5 0.640383 6 2 --> 8 0.036762 6 3 --> 7 0.165081 6 4 --> 6 0.153948 6 4 --> 7 0.001227 Total overlap for state 6 = 0.999524 7 2 --> 6 0.003469 7 2 --> 7 0.330419 7 3 --> 5 0.327180 7 3 --> 6 0.020226 7 3 --> 7 0.143415 7 4 --> 5 0.008318 7 4 --> 6 0.145530 7 4 --> 7 0.020683 Total overlap for state 7 = 0.999601 8 2 --> 6 0.331049 8 2 --> 7 0.003453 8 3 --> 5 0.008344 8 3 --> 6 0.145310 8 3 --> 7 0.020424 8 4 --> 5 0.322143 8 4 --> 6 0.020828 8 4 --> 7 0.147693 Total overlap for state 8 = 0.999601 END Characterisation of states as Kohn-Sham bands BEGIN TDDFT Spectroscopic Data State Excitation Energy Characterisation Converged Transition Dipoles (x,y,z) 1 6.5473971594196110E+000 Singlet Yes ( -8.1795306121346112E-006 -3.4564089336344694E-005) ( 3.2509688966730899E-005 1.2934755562188371E-006) ( -1.3437677409466886E-005 -5.6089948278215118E-006) 2 6.5477931895610837E+000 Singlet Yes ( -2.1968719137211573E-004 7.0339626864693305E-004) ( 1.0286546711327392E-003 -3.1454865615340270E-003) ( -5.4208674766353590E-004 1.5415051960497653E-003) 3 6.5477959245622372E+000 Singlet Yes ( 1.0381162436738922E-003 3.2752571451736268E-003) ( -5.8452216595283879E-005 1.0536872954158838E-005) ( -3.5243315201338721E-004 -1.5030041786209258E-003) 4 6.9682670362142609E+000 Singlet Yes ( -2.1810910146322535E+000 -1.9091179444076365E+000) ( 8.3433521231804542E-001 -1.7962216514560714E+000) ( 3.9339280289056361E-001 1.7828535226058095E+000) 5 6.9682671623558505E+000 Singlet Yes ( -1.5662744900840448E+000 1.7205383620428409E+000) ( 2.8924977420656792E+000 2.6681152573246208E-001) ( -9.5229913947131817E-001 -9.4845221714943473E-001) 6 6.9687191455611650E+000 Singlet Yes ( 9.1444369167153461E-001 1.0029634036985597E+000) ( 1.2850826696348030E+000 1.2827320593679135E+000) ( 2.1774767906530905E+000 2.4030870284027319E+000) 7 7.2396275937532941E+000 unknown No ( -3.7375143373481468E-003 -1.4199767934261615E-003) ( 4.0335791099632701E-005 -3.2195054031300407E-004) ( 1.5911270043209580E-003 8.2897222000213877E-004) 8 7.2396370165366069E+000 unknown No ( -3.5721672861921752E-004 -7.8153744071166042E-004) ( 7.7446002261710029E-005 3.8407175453285536E-003) ( 1.5684794513495109E-004 -1.9778246154052992E-003) END TDDFT Spectroscopic Data