PHACMP calculates the mean difference and the weighted mean difference in the
phase values, in degrees, for reflections. The estimated standard deviations in
the differences are also calculated. The calculations are done as a function of
"d" spacing, resolution, in equal volumes of reciprocal space. In addition,
counts are made of the values of the phases in both sets as a function of
angle. The number of resolution intervals and the range of angle for counts are
under user control. Statistics are done only for those reflections which have
established phases in both sets. Reflections for which the value of the phase
is undetermined in either set are rejected.

All input phases from whatever source are reduced to degrees modulo 360. The
differences in phases are defined as acos(cos(p1-p2)) in order to place them
all in the range 0° to 180°. Note that the sign of the difference is
lost by this method.

The use of this program requires the specification of the two different phase
types to be compared. This is accomplished by the use of the
**phaso1** and **phaso2** lines (PHA SOurce) which
specify the source of phase information in terms of the types specified to
exist in a bdf. The recognized mnemonics are:

**fc**

The calculated structure factor; items n700 or n801 and n802 in
*lrrefl:*, n is the data set number.

**best** **m**

The "best Fourier coefficient" for the "native" or "parent" substance; items
701 and 702 + (m-1)*4, in *lrrefl:*, m is the alternate solution
number.

**most** **m**

The "most probable Fourier coefficient" for the "native" or "parent"
substance; items 701 and 702 + (m-1)*4, in *lrrefl:*, m is the alternate
solution number.

**dens**

The calculated phase from density modification methods; item n511 in
*lrrefl:*, n is the data set number.

**dir** **m**

Direct methods structure factor estimate; items n631 + (m-1)*2, in
*lrrefl:*, where n is the data set number and m is the alternate solution
number.

If the two sets are to be input from different bdf's, the second phase set is
assumed to reside on a bdf with the extension specified with the ext option
(default is PH2). If the second phase set is for a different
compound with a different compid, then this must be specified with the option
**cid** on the PHACMP line.

Reads input archive bdf for phase set 1, and optionally phase set 2.

Optionally, reads phase set 2 from a bdf specified with the options
**cid** and **ext**

** title compare FC phase sets for tridi and tridi1**

** COMPID tridi**

** PHACMP list 50 cid tridi2 ext aa1 bin 11.25 shel 10**

** phaso1 fc**

** phaso2 fc**

In this example the the phase set of tridi on the input archive bdf is
compared with the phase set on the bdf with extension aa1 for the
compound tridi2. Every fiftieth reflection will be listed. The
statistics will be made in ten equal volumes of reciprocal space. Counts will
be made of the number of reflections having phase values in "bins" from
-5.625° to 5.625°, 5.625° to 16.875°, ....,and
343.125° to 354.375°. Counts of differences will be made up through
180°.