LCOV - code coverage report
Current view: top level - membranefusion - FusionPoreExpansionP.cpp (source / functions) Hit Total Coverage
Test: plumed test coverage Lines: 138 158 87.3 %
Date: 2026-03-30 13:16:06 Functions: 6 7 85.7 %

          Line data    Source code
       1             : /* +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
       2             : Copyright (c) 2022.
       3             : 
       4             : CVs originally developed by the Jochen Hub group from the University of Saarland (Germany)
       5             : and adapted and implemented in PLUMED by Ary Lautaro Di Bartolo and Diego Masone from the
       6             : National University of Cuyo (Argentina).
       7             : 
       8             : The membranefusion module is free software: you can redistribute it and/or modify
       9             : it under the terms of the GNU Lesser General Public License as published by
      10             : the Free Software Foundation, either version 3 of the License, or
      11             : (at your option) any later version.
      12             : 
      13             : The membranefusion module is distributed in the hope that it will be useful,
      14             : but WITHOUT ANY WARRANTY; without even the implied warranty of
      15             : MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      16             : GNU Lesser General Public License for more details.
      17             : 
      18             : You should have received a copy of the GNU Lesser General Public License
      19             : along with plumed.  If not, see <http://www.gnu.org/licenses/>.
      20             : +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ */
      21             : #include "colvar/Colvar.h"
      22             : #include "core/ActionRegister.h"
      23             : #include <cmath>
      24             : #ifdef _OPENMP
      25             : #if _OPENMP >= 201307
      26             : #include <omp.h>
      27             : #endif
      28             : #endif
      29             : 
      30             : namespace PLMD {
      31             : namespace membranefusion {
      32             : //+PLUMEDOC MEMBRANEFUSIONMOD_COLVAR FUSIONPOREEXPANSIONP
      33             : /*
      34             : A CV for inducing the expansion of a fusion pore from a nucleated fusion pore.
      35             : 
      36             : Calculate the collective variable designed by Hub \cite Hub2021  and implemented into PLUMED by Masone and collaborators.
      37             : This CV is capable of inducing the expansion of the fusion pore from a nucleated fusion pore.
      38             : 
      39             : \f[
      40             : \xi_e = \frac{R(r) - R_0}{R_0}
      41             : \f]
      42             : 
      43             : Where \f$\xi_e\f$ is the CV, \f$R_0\f$ is a normalization constant that makes zero the initial value of \f$\xi_e\f$, and
      44             : \f$R(r)\f$ is the approximate radius of the fusion pore, which is defined by the number of waters and phosphateoxygens
      45             : beads within a horizontal layer in the center of both membranes.
      46             : 
      47             : \par Examples
      48             : 
      49             : This example induces the expansion of a nucleated fusion pore (\f$\xi_e = 0.75\f$) from a just nucleated fusion pore (\f$\xi_e = 0.00\f$).
      50             : 
      51             : \plumedfile
      52             : lMem: GROUP ATOMS=1-10752,21505-22728,23953-24420 #All the lower membrane beads.
      53             : uMem: GROUP ATOMS=10753-21504,22729-23952,24421-24888 #All the upper membrane beads.
      54             : tails: GROUP ATOMS=8-23948:12,12-23952:12,23966-24884:18,23970-24888:18 #All the lipid tails beads (from the lower and upper membrane).
      55             : waters: GROUP ATOMS=24889-56589  #All the water beads.
      56             : po4: GROUP ATOMS=2-23942:12,23957-24875:18 #All the lipid phosphateoxygens beads.
      57             : 
      58             : fusionPoreExpansion: FUSIONPOREEXPANSIONP UMEMBRANE=uMem LMEMBRANE=lMem TAILS=tails WATERS=waters PHOSPHATEOXYGENS=po4 NSMEM=85 D=7.0 R0=0.57
      59             : 
      60             : MOVINGRESTRAINT ...
      61             :     ARG=fusionPoreExpansion
      62             :     STEP0=0 AT0=0.0 KAPPA0=10000.0
      63             :     STEP1=500000 AT1=0.75 KAPPA1=10000.0
      64             : ...
      65             : 
      66             : PRINT ARG=fusionPoreExpansion FILE=COLVAR STRIDE=1
      67             : 
      68             : \endplumedfile
      69             : 
      70             : */
      71             : //+ENDPLUMEDOC
      72             : class fusionPoreExpansionP : public Colvar {
      73             :   std::vector<AtomNumber> UMEM, LMEM, TAILS, WATERS, POXYGENS;
      74             :   std::vector<double> NSMEM, DSMEM, HMEM, VO, D, H, RMAX, R0, XCYL, YCYL;
      75             : 
      76             : public:
      77             :   explicit fusionPoreExpansionP(const ActionOptions &);
      78             :   void calculate() override;
      79             :   static void registerKeywords(Keywords &keys);
      80             : };
      81             : 
      82       13787 : PLUMED_REGISTER_ACTION(fusionPoreExpansionP, "FUSIONPOREEXPANSIONP")
      83             : 
      84           5 : void fusionPoreExpansionP::registerKeywords(Keywords &keys) {
      85           5 :   Colvar::registerKeywords(keys);
      86          10 :   keys.add("atoms", "UMEMBRANE", "all the beads of the upper membrane.");
      87          10 :   keys.add("atoms", "LMEMBRANE", "all the beads of the lower membrane.");
      88          10 :   keys.add("atoms", "TAILS", "all the tail beads of the system.");
      89          10 :   keys.add("atoms", "WATERS", "all the water beads of the system.");
      90          10 :   keys.add("atoms", "PHOSPHATEOXYGENS", "all the lipid phosphateoxygens beads of the system.");
      91          10 :   keys.add("compulsory", "NSMEM", "the number of slices of the membrane fusion cylinder.");
      92          10 :   keys.add("optional", "DSMEM", "( default=0.1 ) thickness of the slices of the membrane fusion cylinder.");
      93          10 :   keys.add("optional", "HMEM", "( default=0.25 ) parameter of the step function θ(x,h) for the membrane fusion.");
      94          10 :   keys.add("optional", "VO", "( default=0.076879 ) beads' molecular volume.");
      95          10 :   keys.add("compulsory", "D", "horizontal layer thickness, it depends on the Z separation of the membranes.");
      96          10 :   keys.add("optional", "H", "( default=0.1 ) parameter of the step function θ(x,h) for the fusion pore expansion.");
      97          10 :   keys.add("optional", "RMAX", "( default=2.5 ) to avoid effects of membrane undulations in large membranes (more than 256 lipids).");
      98          10 :   keys.add("compulsory", "R0", "normalization constant that makes 0 the initial value of the CV.");
      99          10 :   keys.add("optional", "XCYL", "X coordinate of the fixed cylinder, if not present this will be calculated.");
     100          10 :   keys.add("optional", "YCYL", "X coordinate of the fixed cylinder, if not present this will be calculated.");
     101           5 : }
     102             : 
     103           1 : fusionPoreExpansionP::fusionPoreExpansionP(const ActionOptions &ao) : PLUMED_COLVAR_INIT(ao) {
     104           2 :   parseAtomList("UMEMBRANE", UMEM);
     105           1 :   if (UMEM.size() == 0) {
     106           0 :     error("UMEMBRANE has not any atom specified.");
     107             :   }
     108             : 
     109           2 :   parseAtomList("LMEMBRANE", LMEM);
     110           1 :   if (LMEM.size() == 0) {
     111           0 :     error("LMEMBRANE has not any atom specified.");
     112             :   }
     113             : 
     114           2 :   parseAtomList("TAILS", TAILS);
     115           1 :   if (TAILS.size() == 0) {
     116           0 :     error("TAILS has not any atom specified.");
     117             :   }
     118             : 
     119           2 :   parseAtomList("WATERS", WATERS);
     120           1 :   if (WATERS.size() == 0) {
     121           0 :     error("WATERS has not any atom specified.");
     122             :   }
     123             : 
     124           2 :   parseAtomList("PHOSPHATEOXYGENS", POXYGENS);
     125           1 :   if (POXYGENS.size() == 0) {
     126           0 :     error("PHOSPHATEOXYGENS has not any atom specified.");
     127             :   }
     128             : 
     129           2 :   parseVector("NSMEM", NSMEM);
     130           1 :   if (NSMEM.size() > 1) {
     131           0 :     error("NSMEM cannot take more than one value.");
     132             :   }
     133             : 
     134           2 :   parseVector("DSMEM", DSMEM);
     135           1 :   if (DSMEM.size() > 1) {
     136           0 :     error("DSMEM cannot take more than one value.");
     137             :   }
     138           1 :   if (DSMEM.size() == 0) {
     139           0 :     DSMEM.push_back(0.1);
     140             :   }
     141             : 
     142           2 :   parseVector("HMEM", HMEM);
     143           1 :   if (HMEM.size() > 1) {
     144           0 :     error("HMEM cannot take more than one value.");
     145             :   }
     146           1 :   if (HMEM.size() == 0) {
     147           0 :     HMEM.push_back(0.25);
     148             :   }
     149             : 
     150           2 :   parseVector("VO", VO);
     151           1 :   if (VO.size() > 1) {
     152           0 :     error("VO cannot take more than one value.");
     153             :   }
     154           1 :   if (VO.size() == 0) {
     155           0 :     VO.push_back(0.076879);
     156             :   }
     157             : 
     158           2 :   parseVector("D", D);
     159           1 :   if (D.size() > 1) {
     160           0 :     error("D cannot take more than one value.");
     161             :   }
     162             : 
     163           2 :   parseVector("H", H);
     164           1 :   if (H.size() > 1) {
     165           0 :     error("H cannot take more than one value.");
     166             :   }
     167           1 :   if (H.size() == 0) {
     168           0 :     H.push_back(0.1);
     169             :   }
     170             : 
     171           2 :   parseVector("RMAX", RMAX);
     172           1 :   if (RMAX.size() > 1) {
     173           0 :     error("RMAX cannot take more than one value.");
     174             :   }
     175           1 :   if (RMAX.size() == 0) {
     176           0 :     RMAX.push_back(2.5);
     177             :   }
     178             : 
     179           2 :   parseVector("R0", R0);
     180           1 :   if (R0.size() > 1) {
     181           0 :     error("R0 cannot take more than one value.");
     182             :   }
     183             : 
     184           2 :   parseVector("XCYL", XCYL);
     185           1 :   if (XCYL.size() > 1) {
     186           0 :     error("XCYL cannot take more than one value.");
     187             :   }
     188           1 :   if (XCYL.size() == 0) {
     189           1 :     XCYL.push_back(-1.0);
     190             :   }
     191             : 
     192           2 :   parseVector("YCYL", YCYL);
     193           1 :   if (YCYL.size() > 1) {
     194           0 :     error("YCYL cannot take more than one value.");
     195             :   }
     196           1 :   if (YCYL.size() == 0) {
     197           1 :     YCYL.push_back(-1.0);
     198             :   }
     199             : 
     200           1 :   checkRead();
     201             : 
     202             :   std::vector<AtomNumber> atoms;
     203       12445 :   for (unsigned i = 0; i < UMEM.size(); i++) {
     204       12444 :     atoms.push_back(UMEM[i]);
     205             :   }
     206       12445 :   for (unsigned i = 0; i < LMEM.size(); i++) {
     207       12444 :     atoms.push_back(LMEM[i]);
     208             :   }
     209        4097 :   for (unsigned i = 0; i < TAILS.size(); i++) {
     210        4096 :     atoms.push_back(TAILS[i]);
     211             :   }
     212       31800 :   for (unsigned i = 0; i < WATERS.size(); i++) {
     213       31799 :     atoms.push_back(WATERS[i]);
     214             :   }
     215        2049 :   for (unsigned i = 0; i < POXYGENS.size(); i++) {
     216        2048 :     atoms.push_back(POXYGENS[i]);
     217             :   }
     218             : 
     219           1 :   addValueWithDerivatives();
     220           1 :   setNotPeriodic();
     221           1 :   requestAtoms(atoms);
     222           1 : }
     223           4 : void fusionPoreExpansionP::calculate() {
     224             :   /*************************
     225             :   *                        *
     226             :   *         System         *
     227             :   *                        *
     228             :   **************************/
     229             : 
     230             :   // Box dimensions.
     231           4 :   double Lx = getBox()[0][0], Ly = getBox()[1][1], Lz = getBox()[2][2];
     232             : 
     233             :   // Z center of the upper membrane (uMem) and lower membrane (lMem) for systems with PBC: https://en.wikipedia.org/wiki/Center_of_mass#Systems_with_periodic_boundary_conditions .
     234             :   double ZuMem, ZuMemcos = 0.0, ZuMemsin = 0.0, uMemAngle, ZlMem, ZlMemcos = 0.0, ZlMemsin = 0.0, lMemAngle;
     235             : 
     236             : #ifdef _OPENMP
     237             : #if _OPENMP >= 201307
     238           4 :   #pragma omp parallel for private(uMemAngle, lMemAngle) reduction(+:ZuMemcos, ZuMemsin, ZlMemcos, ZlMemsin)
     239             : #endif
     240             : #endif
     241             :   for (unsigned i = 0; i < UMEM.size(); i++) {
     242             :     uMemAngle = 2.0 * M_PI * getPbc().realToScaled(pbcDistance(Vector(0.0, 0.0, 0.0), getPosition(i)))[2];
     243             :     lMemAngle = 2.0 * M_PI * getPbc().realToScaled(pbcDistance(Vector(0.0, 0.0, 0.0), getPosition(i + UMEM.size())))[2];
     244             :     ZuMemcos += cos(uMemAngle);
     245             :     ZuMemsin += sin(uMemAngle);
     246             :     ZlMemcos += cos(lMemAngle);
     247             :     ZlMemsin += sin(lMemAngle);
     248             :   }
     249           4 :   ZuMemcos = ZuMemcos / UMEM.size();
     250           4 :   ZuMemsin = ZuMemsin / UMEM.size();
     251           4 :   ZuMem = Lz * (atan2(-ZuMemsin, -ZuMemcos) + M_PI) / (2.0 * M_PI);
     252           4 :   ZlMemcos = ZlMemcos / UMEM.size();
     253           4 :   ZlMemsin = ZlMemsin / UMEM.size();
     254           4 :   ZlMem = Lz * (atan2(-ZlMemsin, -ZlMemcos) + M_PI) / (2.0 * M_PI);
     255             : 
     256             :   // Z center of the boths membranes (upper and lower).
     257           4 :   double ZMems = (ZuMem + ZlMem) / 2.0;
     258             : 
     259             :   /**************************
     260             :   *                         *
     261             :   *   Xcyl_Mem & Ycyl_Mem   *
     262             :   *                         *
     263             :   ***************************/
     264             : 
     265             :   // Quantity of beads of the membranes.
     266           4 :   unsigned membraneBeads = UMEM.size() + LMEM.size();
     267             : 
     268             :   // Z distance from the lipid tail to the geometric center of both membranes.
     269             :   double ZTailDistance;
     270             : 
     271             :   // Z position of the first slice.
     272           4 :   double firstSliceZ_Mem = ZMems + (0.0 + 0.5 - NSMEM[0] / 2.0) * DSMEM[0];
     273             : 
     274             :   // Z distance between the first slice and the Z center of the membrane.
     275           4 :   double firstSliceZDist_Mem = pbcDistance(Vector(0.0, 0.0, firstSliceZ_Mem), Vector(0.0, 0.0, ZMems))[2];
     276             : 
     277             :   // Position in the cylinder.
     278             :   double PositionS_Mem;
     279             : 
     280             :   // Slices to analyze per particle.
     281             :   unsigned s1_Mem, s2_Mem;
     282             : 
     283             :   // Eq. 7 Hub & Awasthi JCTC 2017.
     284           4 :   std::vector<double> faxial_Mem(TAILS.size() * NSMEM[0]);
     285             : 
     286             :   // Eq. 10 Hub & Awasthi JCTC 2017.
     287           4 :   std::vector<double> Fs_Mem(NSMEM[0]);
     288             : 
     289             :   // Eq. 11 Hub & Awasthi JCTC 2017.
     290           4 :   std::vector<double> ws_Mem(NSMEM[0]);
     291             : 
     292             :   // Eq. 10 Hub & Awasthi JCTC 2017.
     293             :   double W_Mem = 0.0;
     294             : 
     295             :   // Eq. 21 and 22 Hub & Awasthi JCTC 2017.
     296           4 :   std::vector<double> sx_Mem(NSMEM[0]), sy_Mem(NSMEM[0]), cx_Mem(NSMEM[0]), cy_Mem(NSMEM[0]);
     297             : 
     298             :   // Eq. 10 Hub & Awasthi JCTC 2017.
     299             :   double Xsc_Mem = 0.0, Xcc_Mem = 0.0, Ysc_Mem = 0.0, Ycc_Mem = 0.0;
     300             : 
     301             :   // Aux.
     302             :   double x, aux;
     303             : 
     304             :   // Scaled position of the lipid tail respect the origin of coordinates.
     305           4 :   Vector TailPosition;
     306             : 
     307             : #ifdef _OPENMP
     308             : #if _OPENMP >= 201307
     309             :   #pragma omp declare reduction(vec_double_plus : std::vector<double> : \
     310             :   std::transform(omp_out.begin(), omp_out.end(), omp_in.begin(), omp_out.begin(), std::plus<double>())) \
     311             :   initializer(omp_priv = decltype(omp_orig)(omp_orig.size()))
     312             : #endif
     313             : #endif
     314             : 
     315             : #ifdef _OPENMP
     316             : #if _OPENMP >= 201307
     317           4 :   #pragma omp parallel for private(ZTailDistance, PositionS_Mem, TailPosition, x, aux, s1_Mem, s2_Mem) reduction(vec_double_plus:Fs_Mem, sx_Mem, sy_Mem, cx_Mem, cy_Mem)
     318             : #endif
     319             : #endif
     320             :   for (unsigned i = 0; i < TAILS.size(); i++) {
     321             :     ZTailDistance = pbcDistance(Vector(0.0, 0.0, ZMems), getPosition(i + membraneBeads))[2];
     322             :     PositionS_Mem = (ZTailDistance + firstSliceZDist_Mem) / DSMEM[0];
     323             :     // If the following condition is met the particle is in the Z space of the cylinder.
     324             :     if ((PositionS_Mem >= (-0.5 - HMEM[0])) && (PositionS_Mem <= (NSMEM[0] + 0.5 - 1.0 + HMEM[0]))) {
     325             :       //Defining the slices to analyze each particle.
     326             :       if (PositionS_Mem < 1) {
     327             :         s1_Mem = 0;
     328             :         s2_Mem = 2;
     329             :       } else if (PositionS_Mem <= (NSMEM[0] - 2.0)) {
     330             :         s1_Mem = floor(PositionS_Mem) - 1;
     331             :         s2_Mem = floor(PositionS_Mem) + 1;
     332             :       } else {
     333             :         s1_Mem = NSMEM[0] - 3;
     334             :         s2_Mem = NSMEM[0] - 1;
     335             :       }
     336             : 
     337             :       TailPosition = getPbc().realToScaled(pbcDistance(Vector(0.0, 0.0, 0.0), getPosition(i + membraneBeads)));
     338             : 
     339             :       for (unsigned s = s1_Mem; s <= s2_Mem; s++) {
     340             :         x = (ZTailDistance - (s + 0.5 - NSMEM[0] / 2.0) * DSMEM[0]) * 2.0 / DSMEM[0];
     341             :         if (!((x <= -1.0 - HMEM[0]) || (x >= 1.0 + HMEM[0]))) {
     342             :           if (((-1.0 + HMEM[0]) <= x) && (x <= (1.0 - HMEM[0]))) {
     343             :             faxial_Mem[i + TAILS.size() * s] = 1.0;
     344             :             Fs_Mem[s] += 1.0;
     345             :             sx_Mem[s] += sin(2.0 * M_PI * TailPosition[0]);
     346             :             sy_Mem[s] += sin(2.0 * M_PI * TailPosition[1]);
     347             :             cx_Mem[s] += cos(2.0 * M_PI * TailPosition[0]);
     348             :             cy_Mem[s] += cos(2.0 * M_PI * TailPosition[1]);
     349             :           } else if (((1.0 - HMEM[0]) < x) && (x < (1.0 + HMEM[0]))) {
     350             :             aux = 0.5 - ((3.0 * x - 3.0) / (4.0 * HMEM[0])) + (pow((x - 1.0), 3) / (4.0 * pow(HMEM[0], 3)));
     351             :             faxial_Mem[i + TAILS.size() * s] = aux;
     352             :             Fs_Mem[s] += aux;
     353             :             sx_Mem[s] += aux * sin(2.0 * M_PI * TailPosition[0]);
     354             :             sy_Mem[s] += aux * sin(2.0 * M_PI * TailPosition[1]);
     355             :             cx_Mem[s] += aux * cos(2.0 * M_PI * TailPosition[0]);
     356             :             cy_Mem[s] += aux * cos(2.0 * M_PI * TailPosition[1]);
     357             :           } else if (((-1.0 - HMEM[0]) < x) && (x < (-1.0 + HMEM[0]))) {
     358             :             aux = 0.5 + ((3.0 * x + 3.0) / (4.0 * HMEM[0])) - (pow((x + 1.0), 3) / (4.0 * pow(HMEM[0], 3)));
     359             :             faxial_Mem[i + TAILS.size() * s] = aux;
     360             :             Fs_Mem[s] += aux;
     361             :             sx_Mem[s] += (aux * sin(2.0 * M_PI * TailPosition[0]));
     362             :             sy_Mem[s] += (aux * sin(2.0 * M_PI * TailPosition[1]));
     363             :             cx_Mem[s] += (aux * cos(2.0 * M_PI * TailPosition[0]));
     364             :             cy_Mem[s] += (aux * cos(2.0 * M_PI * TailPosition[1]));
     365             :           }
     366             :         }
     367             :       }
     368             :     }
     369             :   }
     370             : 
     371         344 :   for (unsigned s = 0; s < NSMEM[0]; s++) {
     372         340 :     if (Fs_Mem[s] != 0.0) {
     373         340 :       ws_Mem[s] = tanh(Fs_Mem[s]);
     374         340 :       W_Mem += ws_Mem[s];
     375         340 :       sx_Mem[s] = sx_Mem[s] / Fs_Mem[s];
     376         340 :       sy_Mem[s] = sy_Mem[s] / Fs_Mem[s];
     377         340 :       cx_Mem[s] = cx_Mem[s] / Fs_Mem[s];
     378         340 :       cy_Mem[s] = cy_Mem[s] / Fs_Mem[s];
     379         340 :       Xsc_Mem += sx_Mem[s] * ws_Mem[s];
     380         340 :       Ysc_Mem += sy_Mem[s] * ws_Mem[s];
     381         340 :       Xcc_Mem += cx_Mem[s] * ws_Mem[s];
     382         340 :       Ycc_Mem += cy_Mem[s] * ws_Mem[s];
     383             :     }
     384             :   }
     385             : 
     386           4 :   Xsc_Mem = Xsc_Mem / W_Mem;
     387           4 :   Ysc_Mem = Ysc_Mem / W_Mem;
     388           4 :   Xcc_Mem = Xcc_Mem / W_Mem;
     389           4 :   Ycc_Mem = Ycc_Mem / W_Mem;
     390             : 
     391             :   // Eq. 12 Hub & Awasthi JCTC 2017.
     392             :   double Xcyl_Mem, Ycyl_Mem;
     393             : 
     394           4 :   if ((XCYL[0] > 0.0) && (YCYL[0] > 0.0)) {
     395             :     Xcyl_Mem = XCYL[0];
     396             :     Ycyl_Mem = YCYL[0];
     397             :   } else {
     398           4 :     Xcyl_Mem = (atan2(-Xsc_Mem, -Xcc_Mem) + M_PI) * Lx / (2 * M_PI);
     399           4 :     Ycyl_Mem = (atan2(-Ysc_Mem, -Ycc_Mem) + M_PI) * Ly / (2 * M_PI);
     400             :   }
     401             : 
     402             :   /*************************
     403             :   *                        *
     404             :   *         Xi_Exp         *
     405             :   *                        *
     406             :   **************************/
     407             : 
     408             :   // Quantity of beads that could participate in the calculation of the Xi_Chain
     409           4 :   unsigned chainBeads = WATERS.size() + POXYGENS.size();
     410             : 
     411             :   // Quantity of beads that don't participate in the calculation of the Xi_Chain
     412           4 :   unsigned noChainBeads = (UMEM.size() * 2) + TAILS.size();
     413             : 
     414             :   // Center of the cylinder. X and Y are calculated (or defined), Z is the Z component of the geometric center of the membranes.
     415           4 :   Vector xyzCyl = pbcDistance(Vector(0.0, 0.0, 0.0), Vector(Xcyl_Mem, Ycyl_Mem, ZMems));
     416             : 
     417             :   // Estimation of RO with the Hub 2021 JCTC method. Only needed for the expansion.
     418           4 :   double RO = R0[0];
     419             : 
     420             :   // Number of polar atoms inside the horizontal layer. Eq. 3 Hub 2021 JCTC.
     421             :   double np = 0.0, fz, fr, fz_prime, fr_prime;
     422             : 
     423             :   // Derivative of np. Eq. 8 Hub 2021 JCTC.
     424           4 :   std::vector<double> d_np_dx(chainBeads), d_np_dy(chainBeads), d_np_dz(chainBeads);
     425             : 
     426             :   // Pore radius of the defect. Eq. 2 Hub 2021 JCTC.
     427             :   double poreR = 1.0;
     428             : 
     429             :   // Z center of the Membrane in the RMAX radius.
     430             :   double ZMemRMAX, ZMemRMAXcos = 0.0, ZMemRMAXsin = 0.0, countAux = 0.0, auxcos, auxsin;
     431             : 
     432             :   ZMemRMAX = ZMems;
     433             : 
     434             :   // The curvature of large membranes (1024 lipids) makes the Z-center of the membranes not to be representative
     435             :   // in some sectors, particularly in the region of ​​the defect.
     436             :   //
     437             :   // To solve this, the center Z of the membranes in the defect sector is calculated and used to calculate
     438             :   // the number of polar atoms within the horizontal layer AND in the radious of the defect.
     439             :   //
     440             :   // ________       | |       ________
     441             :   // ________ \_____| |______/ _______<-- Top membrane.
     442             :   //         \______|P|_______/
     443             :   //                |O|
     444             :   //                | |               <-- Z-center of the membranes in the region of the defect.
     445             :   //          ______|R|_______        <-- Z-center of the membranes
     446             :   //         / _____|E|______ \ 
     447             :   //        / /     | |      \ \ 
     448             :   // ______/ /      | |       \ \______
     449             :   // _______/                  \_______<-- Bottom membrane.
     450             : 
     451             :   // Center of mass for systems with PBC: https://en.wikipedia.org/wiki/Center_of_mass#Systems_with_periodic_boundary_conditions
     452           4 :   Vector MemCylDistances, distCylinder;
     453             :   double angle, ri;
     454             : 
     455             : #ifdef _OPENMP
     456             : #if _OPENMP >= 201307
     457           4 :   #pragma omp parallel for private(MemCylDistances, x, angle, auxcos, auxsin) reduction(+:ZMemRMAXcos, ZMemRMAXsin, countAux)
     458             : #endif
     459             : #endif
     460             :   for (unsigned i = 0; i < membraneBeads; i++) {
     461             :   MemCylDistances = pbcDistance(xyzCyl, pbcDistance(Vector(0.0, 0.0, 0.0), getPosition(i)));
     462             :     x = sqrt(pow(MemCylDistances[0], 2) + pow(MemCylDistances[1], 2)) / RMAX[0];
     463             :     if (!((x <= -1.0 - H[0]) || (x >= 1.0 + H[0]))) {
     464             :       angle = 2.0 * M_PI * getPbc().realToScaled(pbcDistance(Vector(0.0, 0.0, 0.0), getPosition(i)))[2];
     465             :       auxcos = cos(angle);
     466             :       auxsin = sin(angle);
     467             :       if (((-1.0 + H[0]) <= x) && (x <= (1.0 - H[0]))) {
     468             :         ZMemRMAXcos += 1.0 * auxcos;
     469             :         ZMemRMAXsin += 1.0 * auxsin;
     470             :         countAux += 1.0;
     471             :       } else if (((1.0 - H[0]) < x) && (x < (1.0 + H[0]))) {
     472             :         ZMemRMAXcos += (0.5 - 0.75 * (x - 1.0) / H[0] + 0.25 * pow((x - 1.0), 3) / pow(H[0], 3)) * auxcos;
     473             :         ZMemRMAXsin += (0.5 - 0.75 * (x - 1.0) / H[0] + 0.25 * pow((x - 1.0), 3) / pow(H[0], 3)) * auxsin;
     474             :         countAux += (0.5 - 0.75 * (x - 1.0) / H[0] + 0.25 * pow((x - 1.0), 3) / pow(H[0], 3));
     475             :       } else if (((-1.0 - H[0]) < x) && (x < (-1.0 + H[0]))) {
     476             :         ZMemRMAXcos += (0.5 + 0.75 * (x + 1.0) / H[0] - 0.25 * pow((x + 1.0), 3) / pow(H[0], 3)) * auxcos;
     477             :         ZMemRMAXsin += (0.5 + 0.75 * (x + 1.0) / H[0] - 0.25 * pow((x + 1.0), 3) / pow(H[0], 3)) * auxsin;
     478             :         countAux += (0.5 + 0.75 * (x + 1.0) / H[0] - 0.25 * pow((x + 1.0), 3) / pow(H[0], 3));
     479             :       }
     480             :     }
     481             :   }
     482             : 
     483           4 :   ZMemRMAXcos = ZMemRMAXcos / countAux;
     484           4 :   ZMemRMAXsin = ZMemRMAXsin / countAux;
     485           4 :   ZMemRMAX = Lz * (atan2(-ZMemRMAXsin, -ZMemRMAXcos) + M_PI) / (2.0 * M_PI);
     486             : 
     487           4 :   xyzCyl = pbcDistance(Vector(0.0, 0.0, 0.0), Vector(Xcyl_Mem, Ycyl_Mem, ZMemRMAX));
     488             : 
     489             : #ifdef _OPENMP
     490             : #if _OPENMP >= 201307
     491           4 :   #pragma omp parallel for private(distCylinder, fz, fz_prime, fr, fr_prime, ri, x) reduction(+:np)
     492             : #endif
     493             : #endif
     494             :   for (unsigned i = 0; i < chainBeads; i++) {
     495             :   distCylinder = pbcDistance(xyzCyl, pbcDistance(Vector(0.0, 0.0, 0.0), getPosition(i + noChainBeads)));
     496             :     fz = 0.0;
     497             :     fz_prime = 0.0;
     498             :     fr = 0.0;
     499             :     fr_prime = 0.0;
     500             : 
     501             :     ri = sqrt(pow(distCylinder[0], 2) + pow(distCylinder[1], 2));
     502             :     x = ri / RMAX[0];
     503             :     if (!((x <= -1.0 - H[0]) || (x >= 1.0 + H[0]))) {
     504             :       if (((-1.0 + H[0]) <= x) && (x <= (1.0 - H[0]))) {
     505             :         fr = 1.0;
     506             :       } else if (((1.0 - H[0]) < x) && (x < (1.0 + H[0]))) {
     507             :         fr = 0.5 - 0.75 * (x - 1.0) / H[0] + 0.25 * pow((x - 1.0), 3) / pow(H[0], 3);
     508             :         fr_prime = (-0.75 / H[0] + 0.75 * pow((x - 1.0), 2) / pow(H[0], 3)) / (RMAX[0] * ri);
     509             :       } else if (((-1.0 - H[0]) < x) && (x < (-1.0 + H[0]))) {
     510             :         fr = 0.5 + 0.75 * (x + 1.0) / H[0] - 0.25 * pow((x + 1.0), 3) / pow(H[0], 3);
     511             :         fr_prime = (0.75 / H[0] - 0.75 * pow((x + 1), 2) / pow(H[0], 3)) / (RMAX[0] * ri);
     512             :       }
     513             : 
     514             :       x = distCylinder[2] * 2.0 / D[0];
     515             :       if (!((x <= -1.0 - H[0]) || (x >= 1.0 + H[0]))) {
     516             :         if (((-1.0 + H[0]) <= x) && (x <= (1.0 - H[0]))) {
     517             :           fz = 1.0;
     518             :         } else if (((1.0 - H[0]) < x) && (x < (1.0 + H[0]))) {
     519             :           fz = 0.5 - 0.75 * (x - 1.0) / H[0] + 0.25 * pow((x - 1.0), 3) / pow(H[0], 3);
     520             :           fz_prime = (-0.75 / H[0] + 0.75 * pow((x - 1.0), 2) / pow(H[0], 3)) * 2.0 / D[0];
     521             :         } else if (((-1.0 - H[0]) < x) && (x < (-1.0 + H[0]))) {
     522             :           fz = 0.5 + 0.75 * (x + 1.0) / H[0] - 0.25 * pow((x + 1.0), 3) / pow(H[0], 3);
     523             :           fz_prime = (0.75 / H[0] - 0.75 * pow((x + 1), 2) / pow(H[0], 3)) * 2.0 / D[0];
     524             :         }
     525             : 
     526             :         np += fz * fr;
     527             :         d_np_dx[i] = fz * fr_prime * distCylinder[0];
     528             :         d_np_dy[i] = fz * fr_prime * distCylinder[1];
     529             :         d_np_dz[i] = fz_prime * fr;
     530             :       }
     531             :     }
     532             :   }
     533           4 :   poreR = sqrt(np * VO[0] / (M_PI * D[0]));
     534             : 
     535             :   // This is the CV that describes the Pore Expansion.
     536           4 :   double Xi_Exp = (poreR - RO) / RO;
     537             : 
     538             :   // Derivatives vector.
     539           4 :   std::vector<Vector> derivatives(chainBeads);
     540             : 
     541             :   // Aux for the derivatives calculations. Eq. 7 Hub 2021 JCTC.
     542             :   double fact2 = 0.0;
     543             : 
     544           4 :   if (poreR != 0.0) {
     545           4 :   fact2 = VO[0] / (2.0 * M_PI * RO * D[0] * poreR);
     546             :   }
     547             : 
     548             :   // Distances from the oxygens to center of the cylinder.
     549           4 :   std::vector<Vector> CylDistances(chainBeads);
     550             : 
     551             : #ifdef _OPENMP
     552             : #if _OPENMP >= 201307
     553           4 :   #pragma omp parallel for
     554             : #endif
     555             : #endif
     556             :   for (unsigned i = 0; i < chainBeads; i++) {
     557             :   derivatives[i][0] = fact2 * d_np_dx[i];
     558             :     derivatives[i][1] = fact2 * d_np_dy[i];
     559             :     derivatives[i][2] = fact2 * d_np_dz[i];
     560             :     CylDistances[i] = pbcDistance(xyzCyl, pbcDistance(Vector(0.0, 0.0, 0.0), getPosition(i + noChainBeads)));
     561             :   }
     562             : 
     563           4 :   Tensor virial;
     564      135392 :   for (unsigned i = 0; i < chainBeads; i++) {
     565      135388 :   setAtomsDerivatives((i + noChainBeads), derivatives[i]);
     566      135388 :     virial -= Tensor(CylDistances[i], derivatives[i]);
     567             :   }
     568             : 
     569           4 :   setValue(Xi_Exp);
     570           4 :   setBoxDerivatives(virial);
     571           4 : }
     572             : }
     573             : }

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