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Title for run (up to 80 characters). Note that this must appear in the data file as a literal string enclosed in quotation marks, e.g. LABEL='TEST RUN'
Reduced mass for collision, m1*m2/(m1+m2), in atomic mass units (mass of carbon-12 is 12.0)
Selects propagator to be used (see Section 1.3 above)
(default 1) If LASTIN is set to 1, the run will terminate after the current scattering calculation is complete. If LASTIN is 0, another complete set of data will be read once this set has been processed.
(default 0). If ICONV is set to 1 on input, NAMELIST block &CONV (see Section 6) will be read and the program will perform automatic convergence testing with respect to step size, RMIN, RMID or RMAX (see Section 2.12). If ICONV = 0 (the default), NAMELIST block &CONV is not read.
(default 0). By default, MOLSCAT will accumulate total cross sections between every pair of levels in the basis set, including closed channels. This uses a fairly large amount of storage, and is often not required. If MXSIG is set to a positive integer, only cross sections between the first MXSIG levels will be calculated.
(default 0). For IOS calculations, these are the highest L and M values for which generalized IOS cross sections, Q(L,M,M') will be accumulated. For ITYPE=103 (see Section 3.3), LMAX and MMAX identify the maximum L for rotors 1 and 2 respectively.
(default 0) If not zero requests that a calculation be restarted from saved S-matrices on unit ISAVEU (see Section 2.5). IRSTRT=3 restarts after the last completed (JTOT,M,INRG)-set found on ISAVEU. IRSTRT=2 restarts after the last completed symmetry block (M) found on ISAVEU; similarly, IRSTRT=1 restarts after a completed JTOT block. If IRSTRT=-1, the program tries to restart at JTOT=JTOTL taken from the current &INPUT data. This option is useful if a job terminates abnormally; it can also be used to change tolerances in the propagator or to switch to a different propagator.
The number of page throws generated is controlled by the parameter ITHROW (default 0). If ITHROW = 1, each new S-matrix calculation starts on a new page.
The printing of total and partial cross sections is controlled by the parameter ISIGPR (default 0). This must be set to 1 if printing of cross sections is required (2 to get coupled states cross sections which are incomplete owing to missing m-values).
If total cross sections are required, there is an alternative form of input flagged by the value JTOTU .ge. 999999 (or JTOTU .lt. JTOTL); this alternative is obtained by the default values. The end of the loop over JTOT is then controlled by the variables DTOL, OTOL and NCAC: JTOT will start at JTOTL and be incremented by JSTEP until NCAC (default 4) successive JTOT values each contribute less that DTOL (default 0.3) to any diagonal cross section matrix element and less than OTOL (default 0.005) to any off-diagonal cross section. (Note that MOLSCAT always gives cross sections in units of square Angstroms.) This option should be used with care, since you must be sure that the calculation will converge before the job runs out of time. Note that elastic cross sections usually converge very much more slowly than inelastic ones.
The loop over symmetry types ("parity cases") M is used differently for different decoupling schemes. For close-coupling, M takes values 1 and 2 for odd and even parity label respectively. (For ITYPE = 3, if the two linear molecules are identical M is further subdivided into exchange symmetries.) For coupled states calculations, M-1 is the body-fixed projection quantum number. Under normal circumstances, MOLSCAT generally loops over all possible values of M for the coupling case concerned (see, however, Section 3.10). If the input variable MSET is non-zero (default 0), MOLSCAT will skip all calculations except for M=MSET. This option is particularly useful for resonance searches (see Section 2.10) and convergence checking (see Section 6). If MHI is also non-zero (default 0), calculations are performed for the range of M values from MSET to MHI.
The units of ENERGY and DNRG are determined by the integer variable EUNITS (default 1) or by the character*4 variable EUNITC (default is blanks) as follows:
EUNITS = 1 or EUNITC = 'CM' 1/cm
EUNITS = 2 or EUNITC = 'K' Kelvin
EUNITS = 3 or EUNITC = 'MHZ' MHz
EUNITS = 4 or EUNITC = 'GHZ' GHz
EUNITS = 5 or EUNITC = 'EV' eV
EUNITS = 6 or EUNITC = 'ERG' erg
EUNITS = 7 or EUNITC = 'AU' Hartrees
EUNITS = 8 or EUNITC = 'KJ' kJ/mol
EUNITS = 9 or EUNITC = 'KCAL' kcal/mol
If a nonblank character string (length 4 or less) is input via EUNITC,
it will override any value input via EUNITS, and an attempt will be
made to match one of the allowed units and set the conversion factor.
This matching is insensitive to case and extraneous characters are
generally ignored, so that EUNITC='1/CM' has the same effect
as EUNITC='cm-1' or EUNITS=1. Likewise, both
EUNITC='e.v.' and EUNITC='eV' cause conversion
from electron volts.
The input energies are converted immediately into 1/cm using the appropriate conversion factor, and all energies subsequently printed by MOLSCAT are in 1/cm.
There are special interpretations of the NNRG and ENERGY parameters which may be invoked when
An alternative form of input is available to facilitate Boltzmann averaging of cross sections using Gaussian quadrature. This is controlled by the array TEMP and the variables NTEMP and NGAUSS. If NTEMP is greater than 0 (default 0), scattering calculations are performed at energies corresponding to NGAUSS point Gaussian quadratures for the NTEMP different temperatures (in Kelvin) in the TEMP array. The maximum allowed values are NTEMP = 5 and NGAUSS = 6. Note that Gaussian quadrature is not a very reliable way of thermally averaging some types of cross sections, and use of this option is generally not recommended.
Early versions of the program saved this in formatted card image files with format statements as indicated below. From MOLSCAT version 11 onwards (June 92), the data are saved in unformatted (binary) files which provide better precision, use less space, and reduce the conversion overhead. In the binary files the data enumerated below are written in the same order, as single (logical) records (i.e. single unformatted WRITE statements), except for (7), which is described more fully below. Beginning with version 14 (Aug 94) NOPEN is found in record (5) rather than in (6).
Contents of the ISAVEU file are as follows:
1.) LABEL,ITYPE,NLEV,NQN,URED,IP (A80/3I4,F8.4,I4)
LABEL = title of run; character length 80.
ITYPE specifies the collision type.
NLEV is the number of levels in the angular basis set.
NQN is the number of (quantum) descriptors per level.
URED is the reduced mass in atomic mass units.
IP is the MOLSCAT version number (14 in this version).
2.) ((JLEV(I,J),I=1,NLEV),J=1,NQN) (20I4)
JLEV(ILEV,J) are the quantum numbers of level ILEV.
The meaning depends on ITYPE; see Section 3.
3.) NLEVEL,(ELEVEL(I),I=1,NLEVEL) (I4/(5E16.8))
Number and values of the asymptotic level energies (1/cm).
4.) NNRG,(ENERGY(I),I=1,NNRG) (I4/(5E16.8))
Number and values of the scattering energies (1/cm).
(NOTE: beginning in version 14 (Aug 94) NOPEN has been moved from
record (6) to record (5), and programs which process saved
S-matrices should check the value of IP in record (1) to
determine the expected format.)
5.) JTOT,INRG,EN,IEXCH,WT,M,NOPEN (2I4,E16.8,I4,E16.8,I4)
These describe a single scattering calculation:
JTOT is the total angular momentum.
INRG is the index of the energy in the list in 4.).
EN is the total energy (1/cm);it should equal ENERGY(INRG).
IEXCH is the exchange parity for identical molecules
IEXCH = 0: no exchange symmetry
IEXCH = 1: odd exchange symmetry
IEXCH = 2: even exchange symmetry
WT (if nonzero) is a statistical weight of this JTOT, M.
M is the serial index of the symmetry block.
NOPEN is the number of open channels in the S-matrix.
6.) (LEV(I),L(I),WV(I),I=1,NOPEN) (I4/(2I4,E16.8))
LEV(I) is a pointer to JLEV (see above) for the basis
set in channel I.
L(I) is the orbital angular momentum for channel I.
WV(I) is the wavevector of channel I (1/Angstroms).
7.) (SREAL(I),I=1,NSQ),(SIMAG(I),I=1,NSQ) (5E16.8)
NSQ=NOPEN*NOPEN
SREAL(I) and SIMAG(I) are the real and imaginary parts
of the S-matrix elements, listed in FORTRAN storage order
for the NOPEN*NOPEN matrices SREAL and SIMAG. In unformatted
files (version 11 and later), SREAL and SIMAG are each
written as a single record, listing only the lower triangle,
((S(I,J),J=1,I),I=1,NOPEN)
These arrays are written by calls to subroutine SWRITE, and
it is recommended that entry SREAD in that routine can be
used to read the records for subsequent processing.
5.), 6.) and 7.) are repeated for each S-matrix calculated,
looping over INRG (innermost), M and JTOT (outermost):
JTOT = JTOTL,JTOTU,JSTEP
M = 1,MXPAR
INRG = 1,NNRG
5.), 6.), 7.)
END LOOP
MXPAR depends on ITYPE. Note that not every S-matrix will necessarily exist. S-matrices may be missing from the file because there are no open channels for that energy, because it was skipped owing to IFEGEN.gt.1 in a pressure broadening calculation, or because there was an error or convergence failure in the calculation.
The S-matrix output file is not supported for IOS calculations, and the output that can be generated for some cases is probably not generally useful.
Note that this option saves CPU time at the expense of disc I/O. It is usually advantageous for the R-matrix, VIVS, quasiadiabatic and hybrid Airy propagators if NNRG is not 1, but for the DeVogelaere and basic log-derivative propagators it may not save resources overall unless the potential itself is very expensive to calculate. This is particularly true on fast machines such as CRAYs. Note, however, that ISCRU .gt. 0 saves considerable time for single-channel IOS cases with INTFLG=6, since the computer time for these is usually dominated by potential evaluations.
When searching for and characterising resonances, a propagator scratch file created in one run may be used in a subsequent run to save work. This is described in Section 2.10 below.
The propagator scratch file option is not implemented in the parallel version of MOLSCAT.
Calculations are supported for ITYPE = 1, 2, 3, 5, 6, 7, 11, 12, 15, 16, 17, 21, 22, 25, 26, 27, 31, 101, and 105. The pressure broadening option is invoked if NLPRBR .gt. 0 on input (default 0); the value of NLPRBR specifies the number of spectroscopic lines for which pressure broadening calculations are to be carried out. The lines themselves are specified by the array LINE, of 4*NLPRBR elements. Each successive quartet of elements of LINE indexes the rotor levels involved in the transition, according to the elements of the JLEVEL array described in Section 3. The 4 values indicate JA, JB, JA', JB', where JA-JB is the spectroscopic transition and the primes indicate post- collision values. Note that the "diagonal" values JA=JA' and JB=JB' describe widths and shifts of isolated lines, and off-diagonal values describe collisional transfer of intensity.
Pressure broadening calculations require S-matrix elements involving the initial and final (spectroscopic) levels at the same kinetic (not total) energy. Generation of the necessary total energies is facilitated by the input parameter IFEGEN. If IFEGEN .gt. 0 (default 0), the program will treat the input ENERGY values as kinetic energies, and generate the necessary total energies for the lines requested. If IFEGEN is 0, only those requested lines which can be constructed from the total energies actually specified by NNRG,ENERGY will be calculated. Through version 13 of MOLSCAT, input values of relative kinetic energies in ENERGY were retained in the the list of generated total energies whether they were needed for a requested pressure broadening calculation or not; beginning with version 14 only total energies needed for the requested pressure broadening calculations are retained. Further, beginning with version 14, specifying IFEGEN .gt. 1 will suppress calculations for individual JTOT, INRG, M ("parity case") which do not contribute S-matrices needed for the requested pressure broadening. WARNING: some subset of the state-to-state cross sections may be incorrect (missing some partial wave/parity contributions) if this last option is used.
The tensor order of the spectroscopic transition (i.e., 1 for dipole transitions, 0 for isotropic Raman scattering) is specified in the input array LTYPE. If the default value (-1) is found, LTYPE is calculated from ABS(JA-JB).
A MOLSCAT run to characterise a resonance must deal with only one total angular momentum JTOT and symmetry type M in a given run. Thus, JTOTL and JTOTU must be the same, and the parameter MSET must be set greater than 0 to select the particular symmetry type required.
A special option is available to assist with searching for narrow resonances. If NNRG is given as a negative integer of the form -5*N, with N integral and the energies themselves specified by ENERGY(1) and DNRG, MOLSCAT will perform N groups of 5 equally spaced calculations. After each group, the program will try to interpret the 5 eigenphase sums as the "tail" of a resonance, and estimate the position of the resonance centre. This estimate is then used as the starting point for the next group of 5 energies. This option can be useful in searching for a resonance if a reasonably good estimate of its energy is already available, and may succeed in converging on a narrow resonance from as far as 10**5 widths away. However, convergence is NOT guaranteed, and it is not usually useful to do more than 3 sets of 5 energies in a single run.
Resonance search calculations should usually be done with either the R-matrix propagator or one of the modified log-derivative propagators, since many different energies are always necessary. It is thus always desirable to use the ISCRU option to save energy-independent matrices on a scratch file. For the special case of resonance searches, with JTOTU = JTOTL and MSET .gt. 0, the ISCRU file from one run may be used as input for the next run at a different set of energies. This option is invoked by setting ISCRU negative for the subsequent run(s); the program then expects to find a suitable input file on channel |ISCRU|. It reads the header on this file to check that it contains valid information, and then proceeds with "subsequent energy" calculations for all the energies requested.
DO 840 JTOT = JTOTL,JTOTU,JSTEP
THETA = THETLW + THETST*JTOT
DO 830 M = 1,MXPHI
PHI = PHILW + PHIST*(M-1)
..
..
Scattering calculation for angles THETA, PHI
..
..
830 CONTINUE
840 CONTINUE
Note that, for surface scattering, subsequent energies have a rather non-intuitive meaning, because the threshold energies (K+G)**2 depend on the parallel component of the momentum K. MOLSCAT interprets subsequent energies as having the SAME parallel momentum as the first energy, but a different perpendicular momentum. This corresponds to a change in the polar angle as well as the scattering energy.
1) If IRMSET .gt. 0 on input (default 9), the program will estimate a suitable distance to start propagating, using the criterion that the wavefunction amplitude in all channels should be less than 10**(-IRMSET) at the starting point. A crude semiclassical estimate of the wavefunction is used to make this estimate, which is calculated separately for each JTOT, M (at the first energy only).
2) If there is a centrifugal barrier present, the program checks that all open channels are classically accessible at the RMAX requested, for all energies in the ENERGY list. If necessary, RMAX is increased to the value of R at the furthest classical turning point found in the centrifugal potential for any energy. However, RMAX is never decreased from the input value. For special purposes, this action can be suppressed by setting IRXSET = 0 on input (default 1). However, this is not recommended for general cross section calculations.
Thus, the input value of RMAX is the smallest distance at which the propagator may terminate. The DeVogelaere and R-matrix propagators also check some aspects of convergence internally, and may propagate beyond RMAX under certain circumstances.
It should be noted that propagating out to the centrifugal turning point is NOT necessarily adequate, particularly when calculating elastic integral cross sections or line shift cross sections. It is also important to realise that a value of RMAX which is adequate for low JTOT may not be adequate for high JTOT, and that calculations using too small a value of RMAX may appear to be converged with respect to the partial wave sum when they are not actually converged.
The IALPHA = 0 option can be very efficient, and often requires remarkably few intervals/steps to produce converged results.
For production runs, IV, IVP, IVPP, IPERT and ISHIFT should usually all be .TRUE. This may be forced by setting IDIAG = .TRUE., which overrides any .FALSE. values for the individual variables.
If IVP, IVPP or ISHIFT is set, VIVS will require radial derivatives of the potential. These are supplied properly for simple potentials by the standard version of POTENL described below, but for some potentials they can be difficult to evaluate. In this case, the input variable NUMDER may be set .TRUE., in which case the necessary derivatives are calculated numerically, and POTENL is never called with IC .gt. 0 (see Section 5).
The Airy propagator is used to propagate from RMID to RMAX. If RMID is greater than RMAX this propagator is not called. By default the initial step size is taken as the value calculated for the modified log-derivative part, but it can be further controlled by the following variables.
On to Section 3